Final Report Summary - EMPHASIS (Explosive Material Production (Hidden) Agile Search and Intelligence System)
Executive Summary:
Detection of explosives has traditionally been focused at the stage when an explosive charge is already ready for use, being transported to or already at the scene of an attack. Preventing terrorist attacks while they are already in motion is extremely difficult. Not only is it difficult to find an explosive on a person or in a bag but one must also face the need to do this in a very short time for countering the attack once a possible suspect or suspicious object has been found. The capability to intervene at an earlier stage is therefore of very high importance. In the preparation phase it is mainly detection of the production that can be carried out. Detection of high vapor pressure explosives themselves could be of importance, but it is more likely that some of the best candidates for detection are the precursors used to make the explosive and possibly also by-products from chemical synthesis that could escape (to air, drains or sewers) during the production process. Basic issues like what substances to look for and where to best look for them are as important as how to look for them. Detection in the preparation phase has several distinct advantages as compared to detection in the phases where an attack is in motion. For example, there is more time available for detection, some detected substances may be present in larger quantities and if a threat is detected, there is time to take further action.
The overall objective with the EMPHASIS project was to test a system concept for detecting ongoing illicit production of explosives and improvised explosive devices (IEDs) in urban areas. The EMPHASIS system is composed of different sensors in a network. Area detectors, strategically positioned, for the monitoring of explosives or precursors to explosives in the vapor phase are used. Multiple static sensors, positioned in the sewer, for the monitoring of the sewage for indicative traces are also used. The detectors are connected in a network and the total gathered data is fused and evaluated in a command center. If a threat substance is detected in elevated amounts, information about the type, location, time and amount is registered and sent to a command center where further evaluation and appropriate actions is performed. The intention is first to cover a large area that will be reduced step by step to smaller areas. The exact pinpointing of the bomb factory is performed using stand-off detectors that can be transported in mobile equipped units.
The sensors and data system protocols have been validated in the field of the test site at the Swedish Defence Research Agency premises. This has been a most valuable procedure in order to be able to match interfaces with the techniques used. The final experimental demonstration has been performed together with BONAS, a parallel project within EU FP 7. This final event gathered 94 participants from 13 countries including USA. The demonstration showed 15 sensors that were used for precursor/explosive trace detection in relevant scenarios. The central system of the EMPHASIS project could read in sensor data from all the sensors (EMPHASIS and BONAS) and display these on a map relating to where the detection occurred together with other data such as concentrations and time for detection. The compounds detected were emitted from sources in relevant scenarios developed within the EMPHASIS project and deployed in a secure and controlled manner at the closed test site. It can be concluded that the concept of the EMPHASIS system is a viable approach for certain scenarios and that the basic capacity of some specific detection techniques are considered as sufficient. Nevertheless, still there is much room for future technical development work in this field where also other types of detection technologies could be of interest to incorporate into a system of the EMPHASIS type.
Project Context and Objectives:
The discovery of hidden bomb factories is of primary importance in the prevention of terrorist activities. In particular, the first stages of manufacturing of improvised explosive devices (IEDs) can take more time as compared to the successive phases comprising the transport to the target of the IED and execution of the attack. In the early stages of IED preparations for a terrorist attack, investigations can be conducted with fewer time constraints and with greater accuracy than at later stages.
One key aspect in the fight against terror actions with homemade explosives is to prevent the use of ordinary chemicals from being used as precursors to explosives. Home-made explosives (HMEs) are easy to make from readily available materials used for legitimate purposes in everyday life. This availability attracts terrorists and criminals to manufacture and use HMEs since military and commercial explosives are more difficult to come by. The uncontrolled information disseminated via the web and the simultaneous presence of trained persons enables large populations to prepare and build IEDs containing Improvised Explosives (IE). IEs can be realized at home using products that can be bought without any specific authorization (e.g. ammonium nitrate and other chemical substances) and using simple equipment present in ordinary kitchens.
The manufacturing of home-made explosives requires work with starting chemicals that needs to be processed into the right products for the assembly of explosives and bombs. The work could lead to the release of vapours and aerosols to the outdoor air of the clandestine laboratory where wind and urban turbulence will dilute and disperse the traces in the surroundings. Equally as important is the detection of target compounds in the sewage where detection is possible due to that cleaning of production equipment might have been performed.
In order to locate a bomb factory it is necessary to work with a variety of sensors able to detect vapours and aerosols, solid traces of explosives on various objects and compounds that might be flushed into the sewer. The project EMPHASIS has worked with the tasks concerned by developing system prototypes and thus being able to show proof of a principle for this new capability. The monitoring of large areas using a network of sensors with varying capabilities generates a large amount of data that are transmitted via wireless networks to remote computers. At this command central, the type/concentrations of target compounds and position/time for the detection of target compounds are displayed on a map. The compiled data could benefit the decisions of end users in case of a positive alert and advantageously complement to other intelligence that might be at hand.
One of the largest scientific, technological and deployment challenges in the security domain today is the development of systems for localisation of IED manufacturing facilities or prevention of the use or enhanced detection possibilities of commercially available precursor chemicals. The IEDs, that can be prepared in ordinary kitchens, contain explosives that in terrorist attacks give devastating effects. For the law enforcement services there is at present an urgent need for tools that contributes to the early discovery and neutralisation of illicit production of explosives. The most important and concrete contributions from systems such as EMPHASIS with respect to the complex task of locating IED manufacturing facilities or hindering production of home-made explosives are:
• An early warning
• Pinpointing of the location of the bomb factory
• Automatic system
• Less personnel requirements as compared to normal intelligence
• Enhanced HME detection capability
Detection during the production phase gives more time for law enforcement to act without risk for themselves or others.
The mechanisms for the dispersion of explosives or precursors to explosives to the surrounding environment will be different depending on if explosives or IEDs are manufactured. If the explosive must be produced by chemical synthesis from some type of starting substances (solvents and reagents) there is probably a larger chance for emission to the air. The volatility of a compound, reflected by its vapour pressure, is an important factor that influences how much of the compound that will be distributed to the vapour phase. In order to have a manageable working environment in the bomb factory a proper ventilation of the room might be necessary. This could be achieved using kitchen fans and open windows. The ventilation of the room will give dispersion of the explosive vapours to the outdoor environment. For the terrorist attacks in Bali (2002), the bombs used were manufactured by mixing chlorate and aluminium powder. These substances cannot be found in the gaseous phase due to their chemical properties. However, small particles originating from these substances can likely be present in the surrounding environment of the bomb factory. The particles can be transferred and adsorbed to surfaces such as door handles and banisters. Chlorate ions will be present in the sewage if e.g. cleaning of equipment has been performed in the illicit production of these IEDs.
In summary, explosives and precursors to explosives can be emitted via several pathways e.g. via the exhaust of the ventilation system, as well as windows and chimneys and close to these emission points the deposition of the exhaust can lead to a surface coverage of traces. In addition, because of transportation, unpacking and handling of the chemicals, the ground in the vicinity of door and car entries and door-handles at the entries of the location can be covered with traces of precursors/explosives. Furthermore, during the illicit production, traces of precursors and by-products needed for manufacturing of an IED can be present in the sewage from the building.
In EMPHASIS, the focus for the detection is on three types of cases; Detection of explosives/precursors in vapour phase at low concentrations; Detection of explosives/precursors at low concentrations in sewage; Detection of particles (low concentrations) e.g. door-handles or other covered surface. The fusion of sensor data leads to potential alerts.
A key aspect of the EMHPASIS concept is that it can allow efficient intelligence lead assessment of an area of a city in order to establish where, and more crucially when illicit bomb-making activity is occurring. A system based on EMPHASIS can lead to a very significant reduction in surveillance man-power of suspect areas. Critically, when a narrow area or house has been identified as being under suspicion, the system can provide invaluable assistance in the timing of police intervention increasing the chance of successful convictions as a consequence.
The sensors in the EMPHASIS system are capable of detecting explosives at extremely low concentration levels (ppb for vapor detection) where totally five different sensor types have been used; two sensors for the air-monitoring subsystem, one sensor type for the sewage monitoring subsystem and two sensors for the stand-off detection of particle traces.
The air-monitoring subsystem in EMHPASIS is based on the combination of two spectroscopic methods which are resonant Raman scattering and Infra-Red (IR) absorbance. Both methods are based on irradiation of a sample with monochromatic radiation from a laser. The collected and analysed radiation will result in a compound specific spectrum. The advantages with the sensors are that they will be able to monitor very long distances, hundreds of metres, and determine the distance to the target compounds and also the concentration of the compounds at this position.
The homemade bombs manufactured by terrorists often contain compounds such as chlorate, perchlorate, ammonia, nitrate, and hydrogen peroxide. Most of these compounds will be present as ions when dissolved in water (sewage) leading to changes of the pH and the conductivity of the water. These properties can be analysed using ion selective electrodes (ISEs). An ISE is a sensor which converts the activity of a specific ion dissolved in a solution into an electrical potential which can be measured by a voltmeter or pH meter. In EMPHASIS, a bunch of ISEs with different selectivity’s in order to facilitate the detection of a variety of compounds have been used. The detection performance for ISEs is in this project adequate for checking if the concept is viable for detection of precursors to explosives in sewage. It should be regarded as a research tool to understand and verify a proof of principle. Ion selective electrodes have generally a detection limit at the level of mmol/l or lower. In laboratory use, with extensive sample preparation, the limits can be reduced to mol/l levels; however, considering the deployment of sensors in a very contaminated matrix such as sewage these limits cannot be achieved.
The sensors for imaging stand-off detection will enable the detection of particulate traces of explosives and precursors on surfaces such as door handles, mail boxes, exhaust openings or chimneys. The basic principle of the infrared backscattering laser spectroscopy is that organic molecules such as the substances of interest absorb radiation in the infrared spectral region. The objects under investigation in the project were illuminated with laser radiation and the diffusely backscattered radiation was collected and analysed using multivariate analysis. The imaging Raman technique used the same analysis principle, however here the Raman scattered light is detected. The techniques can work in parallel and the fusion of the data from both techniques can reduce false alerts.
The terrorist attack executed on the London Underground July 2005 is a horrible example of the result from the manufacture of home-made explosives. The manufacturing of the bombs for the London Underground were performed in the neighbourhood of Leeds. In contrast to the bombs used on July 7 resulting in many victims and injured people, the bombs used on July 21 all failed giving much material for forensic analyses. The bombs were based on a home-made peroxide system where ordinary commercially available chemicals were bought and further modified in a normal kitchen. Many starting chemicals used for making home-made explosives are volatile. Volatile chemicals are possible to detect in the gaseous phase and could be emitted through open windows and kitchen fan systems. The dispersion to the surrounding air is a function of parameters such as weather conditions and city architecture.
The EMPHASIS project started 2011 and ended technically by the demonstration in September 2014. The EMPHASIS system should be regarded as a technical tool for intelligence gathering, rather than a detection system, meaning that the information obtained should be combined and confirmed with information from other sources to make the most accurate assessment of the situation. EMPHASIS is a project where a system concept was developed and tested.
If an EMPHASIS system had been existing 2005 and had been put into operation before the London bombings, the Leeds bomb factory might have been discovered. Consequently, this would have offered police forces the possibility to intervene and catch the terrorists at an early stage of the terrorist activities. This would then have stopped the attack and many lives would have been saved.
Project Results:
WP2
The objective of WP 2 is to disseminate the results and findings of the EMPHASIS project to the partners, to interested Stakeholders, including end-users, the European Commission, Governments, legislative and inspection bodies, law enforcement agencies and the public. It is also to ensure a market for the EMPHASIS system that is useful and applicable for the end-users.
A public website has been set-up and delivered Month 4 in the project. The website will continuously be updated during the project. All the public deliverables will be available for download via this website. www.emphasis-fp7.eu.
WP3
The objectives for WP3 were to define user requirements, identify the threat substances including a characterization of these threat substances in the environment in which they will have to be detected/monitored, as well as setting up realistic scenarios and a detection strategy for deployment of the EMPHASIS concept.
Based on interactions with potential end users, feedback was received on the end user requirements for the tools to be developed within the EMPHASIS programme. These tools comprise air, sewage and trace monitoring of home-made explosives (HMEs) and precursors needed to illicitly prepare HMEs. In the beginning these end user requirements could not immediately be translated to technical specifications, but later on in the project and after continued contacts with end users during Workshops, this translation could be made.
An update of the threat substance list resulting from the EU FP7 LOTUS program was made and a selection of relatively new threat substances was synthesized and characterized. This resulted in validated data on (internet) recipes and some physical and chemical properties of these threat substances. This also included precursors required for the synthesis of the homemade explosives. Furthermore, simulations with CFD (computational fluid dynamics) were performed and realistic velocities of flow, concentrations, dispersion and expansion of threat substances in sewage could be determined. Because of the huge variety of influencing parameters within sewer channel systems (e.g. flow velocity and filling level), CFD calculations were performed for one model substance spreading in two characteristic discharge cases.
Several terrorist attacks that occurred in the past in the EU (Leeds/London, 2005; Stockholm, 2010; Oslo, 2011) were described in detail, including the timeline going from preparations, procurement of ingredients, manufacturing, transport to the target and the final attack. These attacks formed the basis for deriving realistic scenarios that were used to verify and optimize the different detection techniques under development within EMPHASIS (area monitoring, sewer monitoring and stand-off trace detection). On the basis of interviews with end users, a compilation was prepared of current search strategies and an analysis how the EMPHASIS tools could further contribute to the intelligence and technical support tools that are available today to end users and law enforcement agencies.
WP4
The objective of WP4 was to define target substances in sewage and to build and test a sensor node including detection limits, fouling behaviour, data analysis and integration into the EMPHASIS information network.
In collaboration with WP3 target substances for sewage water have been selected. All substances must be of interest regarding both their usefulness for illicit production of explosives as well as their basic properties making them compatible with sewage water.
The sensor node itself comprised ion-selective electrodes (ISE) as a detection unit.
ISEs from different manufacturers have been selected and were first characterized in de-ionised water to determine their sensitivity towards the chosen threat and benign materials. After successful results, these measurements were repeated in tap water and artificial sewage water according to a recipe from the German Institute of Standardization (DIN). The influence of background matrix composition was evaluated and used to develop models to compensate drifts within the sewage composition.
Concepts for hardening the sensor for sewer water application were developed by investigating the influence of a long-term immersion within standing artificial sewage water to fully enable fouling processes. The response characteristic of the sensor node was recorded before and after a four week immersion time. While fouling products were present alongside with large contamination of the sensing membrane of the electrodes, response characteristics did not change over time. From these experiments an automated cleaning procedure once a week was advised.
In order to determine the probable concentrations of explosives or their precursors, CFD calculations as already mentioned in WP3, helped to understand basic principles of concentration ranges within sewer systems as a function of the distance to the insertion point and the starting concentration and overall amount. These simulations made it possible to assess the performance of the different electrodes and the boundary conditions for the real-world tests.
With these data a model sewage was constructed and the characteristic responses of the electrodes in flowing water were recorded. Detection limits for different substances in constant flow and cross-interferences to benign substances were re-evaluated. The response time of the sensor was compared to the background flow provided by normal sewer systems to ensure compatibility between the sensor and real-world application. Experiments showed that the system was able to cope with different background matrices even such different ones as tap water and artificial sewage. The CFD simulations allowed an estimation at which distance from the insertion point a sensor could reliably detect a given amount of target substance.
Finally, the data acquisition chain was developed. Since COTS electrodes and their respective read-out devices are not meant to work as a multi-electrode sensor system, fusing all data from the different sources into one data file had to be performed. This was done by using serial printing from the read-out devices and redirecting the data into different files. These files were processed to extract and merge to obtain files ready for subsequent data processing. Using several different software solutions (from recording to manipulating and analysing under both Microsoft Windows and Linux on one system) it was possible to develop a solution. Data processing was done by using OriginLabs, Origin including realtime import, automated multi-peak picking and evaluation as well as pattern recognition. The results were then post-processed to fit the requirements of the EMPHASIS router.
The last step in the project was a demonstration at FOI test site in Grindsjön, Sweden. The system was installed in a real world sewer system running autonomously. Environmental conditions were rain and heavy wind, so rain water and organic material such as leaves were brought into the sewer system. Nevertheless the system was able to detect, identify and quantify threat substances while not registering benign substances. It could also be shown that the background matrix (tap water or artificial sewage water) had no influence on the detection performance. The sensor itself was fully integrated into the EMHASIS network and used the set-up router system to send its data to the central system.
WP5
Between month 1 and month 24, Cascade has completed the build, assembly, test and demonstration of 3 Infrared Air Monitoring prototypes based on CT3000 OEM core engine. The various measurement campaigns have been a success and the system prepared and sent for field test and validation at FOI Grindsjön site Sweden.
The final system capability is in terms of the compounds to be detected is listed in a classified report and also as function of available laser wavelengths.
Initial detection was tested in a closed long path configuration to assess limit of detection (LoD) in ppb.m for certain compound of interest. Limit of detection currently ranges between 300ppb.m to <100ppb.m. Open path LoD tested in function of plume size. The measurements obtained at FOI Grindsjön site have been reported in a classified report.
Between month 25 and month 36 the EMPHASIS Infrared Air Monitoring systems have been finalised for the demonstration. The setup was composed of 3 identical Infrared Air Monitoring units in an open path arrangement in a network covering an area. Each system had an open path capability of up to 400m which render them ideal to be strategically positioned covertly on roof top of buildings for the monitoring of explosives or precursors to explosives in the vapour phase during illicit manufacturing.
The system was successfully tested at FOI site, Grindsjön, in October 2013, May 2014 and September 2014. This led to a successful end of project demonstration at the end of September 2014.
The Infrared Air Monitoring system sensors are the first QCL based systems capable of fingerprinting (detecting) and monitoring the concentration down to part per billion (ppb) levels in real time (2Hz detection rate) of several compounds of interest simultaneously. To date, the EMPHASIS works relating to the Infrared Air Monitoring system has resulted in the characterisation, fingerprinting and test of 4 target compounds linked to the illicit manufacturing of improvised explosive devices (IED).
During the demonstration, the Infrared Air Monitoring system was capable of detecting precursors in vapour phase leaking out from the ventilation of a cabin with a kitchen inside (i.e. replicating illicit manufacturing of IED). In the Infrared Air Monitoring system each sensor is based on rapidly chirped quantum cascade lasers operating in atmospheric micro-windows and advanced infra-red detector technology.
During the final demonstration the successful detection of 4 compounds was demonstrated under inclement weather conditions using three Infrared Air Monitoring Systems. Compounds were detected on different beam paths, demonstrating that a network of Open Path Analysers could be successfully used in an urban environment in order to identify likely locations of illicit IED manufacturing activity. When combined with other technologies such as mobile sensors and sewer monitoring, the ability to home in on a threat becomes increases.
Optical system configuration:
Air monitoring subsystem 1 operates in an open path optical configuration of several 100 meter length with signal backscattered from retro reflectors. Cascade and Vigo System S.A. have used optical modelling in ZEMAX software to validate the design.
In order to meet system requirements for accurate beam positioning a variety of different types of detectors have been suggested. Vigo System S.A. considered both flat and immersed detectors in quadrant configuration. The advantage of flat detector array is its high fill factor- having no insensitive gaps it is possible to position small beam spot very accurately. However, flat detectors features too low sensitivity and they are not feasible in this project. The back reflected power reaching the detector is too low to be detectable by flat detector. Therefore, compositions incorporating immersion lens has been considered. Application of a hyperhemispherical lens configuration makes the incoming radiation to increase detector capability by an order of magnitude.
For beam positioning applications there were two solutions with immersion lens considered. The first approach was to assemble four single element detectors with immersion lenses on a sapphire carrier in a quadrant arrangement (Figure 1). The quadrant constitutes the single element optical area. It can be noticed that there are huge spaces between neighbouring detectors. Due to large insensitive gaps this solution was rejected from further analysis.
The second solution utilized four detectors with one immersion lens (Figure 2). This solution has been considered as the most promising one, as featured both, high sensitivity due to application of immersion lens and high fill factor as the 4 elements were very close to each other.
Detector system adaptation:
The UK SME Cascade was working with the Polish SME Vigo System S.A. in order to decrease the current detector noise level and improve the signal to noise ratio and beam pointing stability. The dedicated IR detector was optimized for the specific needs of the Emphasis project (air monitoring subsystem).
The device was integrated in a compact detection module that consists of:
- detector element
- ZnSe window with AR coating
- preamplifier
- Peltier cooler
- cooler controller
The key features of the detector are listed below:
- system returned power has been modelled at 0.1% (0.5mW from 500mW peak)
- the detector technology is based on MCT photoconductive detector (PCQI) in a quadrant arrangement of 4x(1x1 mm) or single element photodiode (PVI)
- the detector is stabilised in temperature by a 3 or 4 stage Peltier element
- immersed optics increase responses
Vigo System S.A. has manufactured few detection module prototypes according to detector system specification and resulting from ZEMAX optical modelling. Both photoconductors and photodiodes were developed because it was not clear which type would be the best one. Photoconductors are mature and reliable devices that can have large active area but they are vulnerable to saturation. Photodiodes offer potentially better performance but long wavelength photodiodes are frequently limited by the tunnel and parasitic impedances. They also show significant 1/f noise in the required frequency range and their active area is limited. The limitations are of technological rather than fundamental nature and can be overcome with device design, growth and processing refinements.
The first detector prototype takes the form of a quadrant detector arrays (photoconductors) to allow active X/Y steering of the TX/RX optics with respect to the retro reflectors insuring constant alignment and optimum signal strength. The second one was based on single element photovoltaic device.
Detector concept:
Implementation of dedicated detector for the air monitoring subsystem system is based on the concept of IR photodetector developed at Vigo System S.A (Figure 3). that relies on integration of optical, detection and electronic function in a monolithic heterostructure chip. The functions are:
- concentration of radiation
- enhanced absorption
- efficient and fast collection
- suppression of thermal generation
- internal photoelectric gain
The basic detector material is HgCdTe graded gap alloy, characterized by outstanding photoelectric and structural properties. Since lattice constant is weakly dependent on composition, the material can be used for complex 3D chips whose regions serve as radiation absorber, minority and majority carrier contacts, optical concentrator, passivation and other purposes.
Manufacturing process:
Emphasis detectors are produced from HgCdTe (MCT) grown by MOCVD AIX-200 epitaxial system for II-VI compounds on GaAs substrate (Figure 4). CdTe buffer is grown on GaAs to reduce strain due to lattice mismatch. Growth is fairly well reproducible in short time frame, its need to be fine-tuned for long term reproducibility. Material is measured, and after acceptance may then be processed into planar photoconductor or MESA-structured photovoltaic detectors. After that, passivation (CdTe) and metallization (Cr-Au) layers are deposited. Wafer is diced with a diamond saw and dies are measured and accepted for immersion lens micropolishing. Active element centring, lens shape and size are controlled. Measured lenses are flip-chip bonded to sapphire chip carrier, then glued to four stages TE cooler and assembled in TO-8 based package. Chip carrier is wire bonded to TO-8 package leads. Desiccant is placed inside the package, device supplied with ZnSe window and backfilled with an inert gas.
Detectors are measured using FTIR spectrometer, blackbody, impedance analyser and I-V characterization tools.
MOCVD growth:
Epitaxial growth of heterostructures for Emphasis detectors has been carried out in the AIX-200 II-VI MOCVD system equipped with gas foil rotation for better composition uniformity (Figure 5). The reactor which consist from a horizontal rectangular duct quartz reactor cell (liner) is enclosed in an outer circular quartz tube. Two separated gas inlet channels are provided to prevent premature gas reactions and dust formation. Hydrogen is used as a carrier gas. Dimethylcadmium (DMCd) and diisopropyltelluride (DIPTe) used as precursors are held in temperature-stabilized baths. Ethyl iodine (EI) is used as a donor and tris-dimethyloaminoarsenic (TDMAAs) as acceptor dopant source. DMCd and EI are delivered through the upper channel while DIPTe and TDMAAs are delivered through the lower channel over the quartz container where elementary mercury is held. The wafer holder was made of SiC coated graphite capable of holding up to two inch diameter substrate. The substrate, GaAs (100)2°→(110) was heated with halogen heaters situated directly underneath the wafer holder.
Hg1–xCdxTe and CdTe layers are grown at ~350ºC with mercury source kept at 210ºC. Typical pressure in reactor during deposition is 500 mbar.
Direct Hg1–xCdxTe growth is difficult due to very different thermodynamic properties of HgTe and CdTe. We applied interdiffused multilayer process (IMP) for Hg1–xCdxTe growth to avoid this problem. IMP gives controllable growth of heterostructures with complex composition and doping profiles. In IMP growth, HgTe and CdTe layers are deposited one after another with period 100–200 nm and homogenized by interdiffusion during growth. Any composition can be achieved this way by proper selection of HgTe and CdTe layer growth times.
HgCdTe structures for Emphasis devices are deposited on GaAs substrates. Time of growth vary from 5 hours to ~12 hours in dependence on the detector type.
Growth begins with CdTe buffer deposition to accommodate lattice mismatch and isolate from unintentional doping from substrate/surface. Buffer is followed by HgCdTe structure having both relatively uniform and graded (gap and doping level) regions. The graded gap regions are obtained by programmed growth.
The practical issue in implementation of the Emphasis devices with MOCVD is significant interface grading caused by Cd/Hg and dopants diffusion at the growth temperature. The diffusion allows using IMP technique, but at the same time prevents from obtaining steep composition and doping profiles. Precise composition and doping shaping requires knowledge of nonlinear Cd, Hg, I and As diffusion parameters in HgCdTe. Unfortunately, the parameters vary with composition, time, dopant concentrations and dislocation density. In practice, growth parameters must be determined in series of growths experiments. The SIMS profiles are invaluable in revealing differences between planned and practical heterostructures.
Characterization of grown structures involves transmittance and reflectance spectroscopy, Hall measurements, thickness from cleavage, SIMS and photoresponse spectroscopy and other techniques.
Dozens of photoconductive and photovoltaic HgCdTe structures were deposited for the detectors in this project with purpose to implement required composition and doping profiles designed by computer simulations.
Mechanical design:
The mechanical design of the detector is based on commercially available TO-8 sub-mounts with soldered miniaturised thermoelectric coolers. Peltier thermoelectric cooler (TEC) is a solid-state active heat pump which transfers heat from one side of the device to the other side against the temperature gradient, with consumption of electrical energy. Hermetically sealed package include active element with monolithic immersion lens and thermistor assembled on a cold finger of TE cooler. The detector enclosure is filled with a mixture of heavy inert gases – krypton and xenon. Package also holds a chemical absorber of residual active gases (water vapour, CO2, oxygen and others), ensuring fault-free device operation for many years. Detector is also equipped with 10 mm diameter ZnSe window: rugged and less vulnerable to rapid temperature changes. The drawback of this material is its 70% transmission due to reflection losses. Two-sided antireflection coating has been suggested for transmission improvement, increasing the parameter above 90% in wide spectral range.
Photoconductor:
Several options of photoconductive detectors for Emphasis air monitoring subsystem have been considered:
- detectors with hyperhemispherical lens with 2.5 mm diameter (PCQI) and different detector temperatures (2TE, 3TE, 4TE)
- non-immersed detector (PCQ)
A comparison of particular detection modules and their parameters were made in the work (Figure 6).
Taking into account that returned signal power is very small, non-immersed detector is useless. An efficient way to achieve an effective concentration of radiation is to immerse the photodetector to a hyperhemispherical lens.
The practical (photoconductor) device was based on MOCVD grown structures. The main work was focused on optimization absorber thickness in order to suppress possible interferences inside the detector. New design should ensure almost full absorption of radiation in a single pass of the absorbing layer. Structure for photoconductor was optimized with analytic simulations and later on grown in VIGO's epitaxial system (Figure 7).
An active element monolithically integrated with hyperhemispherical microlens was mounted directly at the top of TE cooler (Figure 8). In order to achieve minimum temperature of active element sapphire chip carrier was removed. Cooling to 210K was necessary to get required detector performance. This implicates the use of 3- stage Peltier cooler. One of the biggest challenges (from the mounting point of view) was centring the microlens and making of wire connection between metallization pads and TO8 pins.
The quadrant detector is followed by four channel preamplifier, where each channel consists of two amplifying stages. First of them is a transimpedance amplifier, with ability to control the detector biasing voltage and compensate the bias current (to avoid amplifier saturation). The second stage is a noninverting voltage amplifier, with variable gain and output voltage offset compensation. The mentioned above parameters are set independently for each channel. Designing the preamplifier, it was mainly focused on achieving low noise level, low input impedance, stability, in band gain flatness, and reaching sufficient cutoff frequency (around 160 MHz). Due to the small enclosure size, and therefore limited heat dissipation ability, the current consumption must have been reduced, and it is also the reason of very strict supply voltage. The IR module case is designed to cooperate with external radiator attached to the front side of the module, however, if necessary, it is possible to use especially suited radiator and the cooling fan mounted on the enclosure top side (Figure 9). Detection module prototype was sent to Cascade in order to integrate it with air monitoring subsystem.
Photodiode:
The device is a Peltier cooled reverse biased immersed photodiode, based on MOCVD grown HgCdTe heterostructure. It features wide optical (3-11 µm) and electrical (~1 GHz) band along with high sensitivity (D*~1010 cmHz1/2/W for >8 µm wavelength).
The device reflects detector concept developed over the last two decades at Vigo (Figure 10). The device is equipped with an immersion (hyperhemisphere) microlense – infrared (IR) concentrator, monolithically integrated with detection structure, and IR retroreflector so as to further enhance IR absorption and shield against background radiation. The heterostructure is a modified PIN photodiode that consists of a narrow bandgap p-type absorber and wide gap heavily doped contacts: N+ - the contact for electrons and P+ - the contact for holes. The absorber is interfaced to the contacts with graded gap regions. The bandgap of N+ and P+ layers is taken sufficiently large to make thermal generation low and prevent injection of electrons (minority carriers) to the absorber. The composition and doping of the interfaces of the absorber are selected so as to eliminate parasitic barriers for electrons and holes that could impede collection of the photogenerated carriers. The p-type HgCdTe alloy is a material of choice for the fast response which is achieved by fast transport of optically generated charge carriers from absorber to contacts. Low gap heavily doped n+ layer allows for small (10 5 Ω×cm2) contact resistances for all contact metals used (Au, Ti, Cr, In).
Fabrication of the photodiode involves optical and electrical epiwafer characterization, photolithography, etching of mesa structures, passivation of mesa sidewalls, contact metallization, dicing of wafers into chips with single-element devices, preparation of immersion lenses, indium bump bonding to sapphire carriers with metal lead-outs, mounting of the chips on cold finger of Peltier coolers, sealing of detector elements in TO-8 packages filled with xenon or xenon/krypton mixtures (Figure 11).
The detectors are characterized by measurements of current-voltage curves, spectral responsivity, frequency dependent noise and time response. The time response measurements are performed with detectors coupled to microwave 50 Ohm or transimpedance preamplifiers constructed at Vigo System SA. The preamplifiers also provide tunable bias voltage in 0 2 V range. Amplified signals are registered with fast oscilloscope of nominal 8 GHz bandwidth, 40 GS/s single shot sample rate and <9 ps rise time.
Two types of pulsed IR radiation sources are used in the time response measurements (Figure 12):
- quantum cascade lasers (QCL) producing 4-100 ns pulses of monochromatic radiation
- optical parametric oscillator (OPO) as a source of short ~25 ps pulses of radiation, tunable in a wide spectral range from UV to 16 µm
The time response measurements are done under conditions allowing for revealing slow components of time response, i.e. at excitation by long 50 100 ns radiation pulse from QCL or short pulse of sufficiently high intensity from OPO. The time constant of the slower component at the tail of signal pulse is used as a parameter characterizing speed of response for various operating conditions.
Photodiode was integrated with one channel preamplifier. Mechanical design of detection module was adopted to Cascade air monitoring system (Figure 13). The preamplifier implements classic idea of transimpedance preamplifier basing on two RF transistors. First transistor acts as voltage preamplifier in common emitter configuration. The following stage is a buffer and impedance converter in common collector configuration. The whole available preamplifier high cut of frequency is ~ 1.4 GHz. In current design, the top frequency is limited to improve the stability and reduce wideband noise. Negative feedback was introduced, therefore the preamplifier is stable within whole bandwidth, and the frequency response is smooth.
Additional activities within EMPHASIS project; “SMART” IR detection module:
Vigo System S.A. has also developed “SMART” IR detection module, which is especially suitable for testing and development purposes. New module cooperates with intelligent TEC controller and allows the user to configure the following parameters with the PC software or user interface (Figure 14):
- detector bias voltage
- compensation of the bias current
- preamplifier first stage transimpedance
- compensation of the frequency response of the first preamplifier stage
- coupling between first and second preamp stage: AC or DC
- compensation of the output DC offset
- preamp bandwidth
- second stage voltage gain
The SMART IR module also offers the ability of monitoring important voltages in the circuit:
- detector bias voltage
- voltage after the first stage and voltage at the preamplifier output
- supply voltages
- TEC & thermistor lines voltages
Optimisation of wirebonding for VIGO detectors:
Wirebonding is a method used to attach a fine wire, in this case 25 m in diameter, from one connection pad (metallized bond sites on interconnection substrates) to TO8 pin, completing the electrical connection between detector and TO8 pins.
The main stages of wirebonding for VIGO detectors are:
1. Making of electrical connection with a gold wire Ø25 µm between active element of detector and each stage of thermocooler (with using two-component epoxy resin Epotek E415G)
2. Making of electrical connection between the first stage of thermocooler with pins of TO-8 sub-mount with using Epotek E415G
All mentioned above steps are handmade which are time consuming and operator depended. Wirebonding optimisation was an attempt to establish bonding parameters in semi-automatic wirebonder (Figure 15).
This work showed that there is a possibility to make a semi-automatic wire bonding connections for VIGO detectors using Aluminium wire (Figure 16). One of advantages of using aluminium wire is its bondability to TE ceramics substrate.
Wire bonding with gold wire was also evaluated. Unfortunately, gold wire does not stick to ceramics and that is why there is a need to design and manufacture metallization pads on TE ceramics substrates. What is more, bonding surface must be heated which may be dangerous for detector. Semi-automatic wire bonding with gold wire requires more R&D work at the moment.
Summary:
VIGO System S.A. developed and manufactured five IR detection modules for Emphasis air monitoring subsystem. First detection module was based on quadrant photoconductive detector and four others were based on photovoltaic detectors.
Newly developed photodetectors and detection modules extended VIGO System products line (QIP series). QIP is the four channel, transimpedance, AC or DC coupled preamplifier and it is dedicated for BenchTop or OEM laser beam positioning applications.
WP 6
Within the EMPHASIS project work package 6 the goal was to develop and test two imaging stand-off trace detection systems. A Raman-based system tested by FOI and an infrared backscattering based system developed by Fraunhofer IAF.
Active Imaging IR Laser Backscattering Spectroscopy:
The IAF imaging IR standoff detection system is based on laser backscattering spectroscopy. A widely tunable quantum cascade laser is used to illuminate the scene and the backscattered light is detected by a high performance infrared imager. By step-tuning the illumination wavelength and synchronous image acquisition, a hyperspectral image is obtained, where each image layer is associated to a specific illumination wavelength. Thus, each pixel vector corresponds to a backscattering spectrum at a specific location in the scene.
An especially interesting region of the infrared part of the electromagnetic spectrum for the goal of chemical substance identification is the molecular fingerprint region between 7 µm and 10 µm, as most organic substances show characteristic spectra in this range (Figure 17). A further advantage is the transparency of the atmosphere, which is a crucial condition for targeted measurement distance, as well as the high power thresholds established by the legislature for eye-safe laser operation.
The spectral measurement range of the detection system is dominated partly by the spectral cut-off and sensitivity of the IR imager in use, and – maybe even more important – by the tuning range and illumination power of the IR laser in the setup. There are only few laser sources that match the challenging boundary conditions required by the spectroscopy system in this spectral range. In the last few years, Quantum Cascade Lasers have emerged as reliable laser chips that are able to cover the required broad tuning range with high spectral brightness and output power and thus constitute the source of choice for application in the backscattering spectroscopy system. Within the EMPHASIS project a new Hetero-Cascading quantum cascade laser structure has been designed and according active chip material has been produced with a tuning range specifically tailored to optimize detection performance for the target substances defined in the EMPHASIS substance list. During epitaxial growth of the wafer material, two gain regions centered at different wavelength are combined. With this approach in one chip the tuning range can be enhanced by about 50 %. The QCL chips are operated in an external cavity setup in Littrow configuration. The collimated beam of the chips front facet is reflected by an optical grating, which is used as wavelength selective element and mounted on a rotation stage (Figure 18).
One of the key goals for the IR backscattering spectroscopy system in the EMPHASIS project was to extend the measurement distance. This was achieved by mounting a wavelength-customized Ritchey-Chrétien-Cassegrain telescope for collecting the backscattered infrared in a front-looking geometry (Figure 19). The entrance aperture of the new collection optics was enlarged to 12.5” diameter in order to reduce the f-number. This enables high spatial-resolution hyperspectral imaging in the desired distance range. A visible camera was aligned with the infrared imaging optics that yields a calibrated visual image of the scene. This extension both simplifies system operation, and moreover supports the operator by identifying contaminated objects in the scene, that produced positive alarms in the hyperspectral image.
An additional goal within the EMPHASIS project was to broaden the scope of detectable target materials. This included adding pre-cursors of actual explosives like Ammonium Nitrate (AN). IR backscattering spectra of some common explosives like PETN, RDX and TNT was compared to the backscattering spectrum of AN. It was quite obvious, that in the formerly measurable wavenumber range over 1100 cm-1 AN has a fairly even spectrum, that shows far less characteristic features then PETN for instance. It was therefore necessary to extend the system’s spectral measurement range by adding an additional laser illumination module, that covers the spectral range from 1000 cm-1 to 1180 cm-1 (Figure 20).
A crucial part of the imaging IR backscattering detection system lies within evaluation of the resulting spectroscopic measurement data. Though the target material spectra are known as they can be measured in advance and thus a spectral target library is not difficult to establish by measuring the pure target substance on a non-scattering surface, the target material might be spread on a strongly scattering surface in a real-world measurement. In this case, the measured target spectrum is (linearly) mixed with the surface-spectrum. As the substance spectra is not known in a general measurement scenario, un-mixing becomes a non-trivial task and thus effort was put into development of customized target detection algorithms.
Stand-off Imaging Raman Spectroscopy:
During the 1st period of the EMPHASIS project a 532 nm imaging Raman system was tested and validated to be a very promising technique for particulate trace detection of explosives/precursors. However because of the risks to skin and eye associated with the 532 nm laser used, focus was instead shifted to testing the 355 nm eye-safe corresponding system that was built up.
Work performed while building the 355nm system has included: optimisation of imaging algorithms, improvement of GUI, and redesign of optical construction. In the system communication protocol parameters for image acquisition specification have also been set between Fraunhofer IAF and FOI.
FOI has together with a Finnish research company, VTT, developed a UV filter prototype necessary to build a 355 nm imaging Raman system which now allows for detection in the UV range (Figure 21).
In Emphasis, the initial tests of the imaging UV-Raman demonstrator system was performed by measuring sub milligram amounts of ammonium nitrate placed in holes in an aluminum plate. The diameters of the holes measured 1 mm and 0.3 mm respectively (Figure 22). The amount of ammonium nitrate in the larger holes, based on hole-geometry and ammonium nitrate density, is estimated to be about 500 µg while the smaller ones contained below 50 µg. The extracted spectra from the hyper spectral image cube created during the measurement show that it is possible to detect the ammonium nitrate in the smaller holes which is estimated to be about <50 µg (Figure 23).
The prototype filter capability was thoroughly evaluated at FOI during the fall of 2013 and discussions on how to make the filter even more efficient has been performed. VTT has delivered a first filter product and tried to optimize the filter since the first delivery during 2014. In total, three filter prototypes have been manufactured and a fourth was stopped since it did not appear to provide any improvements. There are in total two major versions of technology that has been evaluated.
The work on optimization has not resulted in any more detection sensitive filter product than what was used during the final part of the project. The filter and the imaging UV-Raman system has been tested significantly in the EMPHASIS project and the system used at the final demonstration is the best version that has been achieved and has the capability in the range of the above described.
During the final project demonstration in September 2014 the system was placed inside a building aiming at a car door on ~10 m distance. On and around the door handle different precursor particles were applied and the system detected and identified them. The result was presented by showing where on the target surface the different substances are detected, also the threat level (certainty) was displayed. It has now been shown that the imaging Raman technique also can work in an eye-safe way without sacrificing much of the performance.
Orthogonal Image Analysis:
The UV-Raman and mid-IR-based detection techniques proved to be complementary regarding their sensitivity to different compounds. While both techniques rely on a spectroscopic approach and are therefore in principle able to identify a wide range of different materials, there exist large differences in signal strength as well as in the significance of spectral information gathered from the scattered light for the various compounds of interest. The studied techniques in the EMPHASIS project are both very useful for confirming if explosive traces are deposited on suspicious objects. This type of intelligence is of valuable use for police forces and the different detection principles of the techniques provides a basis for covering a broader range of target compounds that can be detected. In addition, when the capability is overlapping the detection results can be co-supported and thus the confidence of the results will be enhanced. For the IR system, it was found that most compounds provided measurable signals. However, there are strong differences in the significance of the backscattering spectra. For example DNT (precursor to TNT) provides a highly characteristic spectral response, easily distinguishable from TNT, which is more difficult using standoff imaging based on UV Raman. Other examples of substances with “good” IR spectra are HMT or PETN. On the other hand, the spectra of e.g. KNO3 and even more KClO3 show less distinct spectral features, while Ammonium Nitrate ranges somewhere in between. Substances like KClO3 are still identifiable by IR spectroscopy, but the much lower spectral significance will render detection difficult especially on interfering substrate materials. UV Raman that uses a 355 nm laser, on the other hand, gives a very high significance of spectral information for almost all substances but have several orders of magnitudes lower signal strength compared to IR backscattering. The limit here is thus in the effective Raman cross-section for the substances that sets the detection limit. Nitrates and chlorates that are less favorably detected by the IR technique, are the compounds that show best performance for UV Raman, while it encounters difficulties to detect DNT, TNT and some other substances due to the lack of signal intensity. Especially for small trace particles. In the case a 532 nm laser is used, the sensitivity is enhanced to a great extent for compounds such as TNT, PETN, RDX, TATP, ammonium nitrate and chlorates etc. As the two techniques operate at non-overlapping regions of the electromagnetic spectrum, the measurement data is independent as in consequence is the probability of false alarms for each measurement method, alone. Separate data analysis algorithms are applied to the hyperspectral images produced by the two imaging sensors, providing a 2D detection map each. Fusion is then accomplished on the bases of the detection images. This approach also allows introduction of weighting factors on the individual decision outputs to improve the cumulative system sensitivity. This is the fusion level of choice, as the false alarm probabilities of the two system specific data analysis algorithms multiply and hence the cumulative probability of false alarms is vastly reduced. Taking into account the above consideration on substance detectivity, it is inviting to introduce substance specific weighting. This means e.g. that the detection outcome of the IR imaging system can be given greater weight than that of the Raman system for substances that have well distinguishable IR spectra but poor Raman spectra, and vice versa. In addition, this approach allows the hyperspectral image analysis algorithms for each sensor to be optimized to individual requirements that may vary slightly. In the EMPHASIS framework, both the imaging Raman and IR spectroscopy systems communicate detection results via the EMPHASIS network to the central command center, where the data is collected and presented to operations staff. By overlaying the measurement results of the two sensors, the decision fusion implementation is provided inherently.
Optical System Configuration:
Detection performance was increased by measures for beam shaping and despeckling. Instead of using a Gaussian shaped collimated beam, providing high intensity in the center at the cost of a rapidly decreasing S/N ratio towards the outer regions, one would like to work with a homogeneous intensity in the illuminated area, i.e. a top-hat beam. Another deteriorating effect is so-called laser speckles, stemming from the coherent nature of the illuminating light. Interference from scattered light at “rough” surfaces (on the scale of the lasers wavelength) disturbs the image quality. Although appearing like additional noise, this effect is deterministic and will not average out simply by longer measurement times. Instead, many different speckle patterns have to be created by varying the illumination conditions. We addressed both issues by coupling the laser into a home-made narrow rectangular waveguide via a fast scanning, resonantly driven 2D-MEMS mirror, providing both homogenization as well as the necessary angle diversity for the creation of statistically independent speckle patterns. The MEMS scanning periods had to be synchronized with the camera frame rate and projection optics were adapted to the size of the waveguide and the FOV of the telescope optics. The developed method is both fast and provides sufficient optical throughput.
Detector Adaption:
Evaluation of a more cost-effective IR standoff system using micro-bolometric imagers revealed that the currently achievable signal to noise ratio does not provide sufficient data quality for reasonable detection results at this time. However, development progress on both detector and illumination side still renders this option interesting for future cost optimization.
During the EMPHASIS project demonstration, both imaging stand-off detection systems successfully found trace amounts of various explosive precursors placed on different objects, e.g. parts of a parked car at a measurement distance of approximately 15m (Figure 24). Test substances included DNT, HMT, Fertilizer and many others (Figure 25). A full spectroscopic measurement together with the required data processing and analysis amounts to slightly less than 20s for the IR backscattering system. The standoff detection systems proved to be fully operational under near-real world conditions (Figure 26).
WP7
Emphasis Network System:
The main objective for WP7 was to specify and implement the system communication infrastructure to provide the Emphasis system with the necessary functionality for wireless and secure data communication between the different sensors (WP4, WP5 and WP6) and the central system responsible for information management, data fusion and presentation (WP8).
At an early stage of the project a concept study was carried out resulting in an internal report: “Emphasis System Network Concept Study” discussing different radio technologies applicable for the different Emphasis sensors. A specific concern was the sewer sensors considering their locations where wireless radio communication was assumed to be difficult.
During the study some real-life tests were performed including public mobile network devices as well as 27MHz and 455Mhz handheld FM transceivers (Figure 27).
The study concluded that both the transceiver solution and the public GSM network would be sufficient for the Emphasis requirements. In order to simplify the development the study also proposed to only use the GSM network in the project (Figure 28).
Followed by the concept study a system architecture definition was produced resulting in a system design specification.
Partly based on the developments within the predecessor Seventh Framework Programme project LOTUS the design specification defined and specified:
- Common hardware (“Router”) and software used to interface each sensor with a wireless network
- Communication protocols for secure data transfer beween sensors and the central system
In order to be able to utilize as much as possible of existing infrastructure and standards the Emphasis Network System (Figure 29) is based on communication via the public mobile network and as far as possible, uses standards like XML (Extensible Markup Language), NMEA (a GPS data format defined by National Marine Electronics Association) and OpenSSL (open-source implementation of SSL/TLS encryption functionalities).
The Router device developed within WP7 includes:
- An XML-based protocol, common for all different Emphasis sensors (as well as sensors developed within the LOTUS project): the implementation have only two requirements on each sensor:
o A physical Ethernet interface (RJ45/twisted pair)
o A HTTP server delivering XML-formatted data
- Wireless communication facilities in terms of a GSM radio module
- A GPS receiver for real-time positioning
- Environmental sensors for real-time collection of temperature and air humidity
- Storage space for collection of data in a case of interrupted wireless communication
- Software for data transfer between sensor-router and router-central system
- Software for encryption/decryption of data
- A web-based configuration interface
A total of ten new Emphasis Routers (Figure 30) were assembled and in addition three Routers inherited from the LOTUS project were updated both hardware- and software-wise to comply with Emphasis requirements.
The first version of the Network System was tested during an on-site field-trial session at FOI in Sweden in October of 2013. The field-trial involved the Cascade IR-sensor, Fraunhofer-ICT sewer sensors and Routers with measurement sources in the form of vapours from HME-manufacturing and sewer water contaminated with residuals from HME-manufacturing. Live sensor data was also transferred to the central system developed and managed by TNO.
The tests resulted in software updates and also revealed the need for data communication simulation software. The simulation software developed from late 2013 to early 2014 not only simplified the Router communication software development but also the sensor integration efforts.
During the first part of 2014 the partners developing sensors (Cascade, Fraunhofer-IAF, Fraunhofer-ICT and FOI) were supplied with Router hardware for final integration with the different sensors. In this period the complete network system was also verified, documented in a System test and verification report.
At the final Emphasis demonstration in late September of 2014 eleven different sensors/routers were deployed simultaneously and sending live data to the central system presented at the test site in real-time.
A summary of the results from WP7:
- It is possible to build a highly scalable, wireless, low-power, sensor network at a low cost using existing components and infrastructure
- The idea of connecting sensors in a scalable network adds a lot of value in terms of real-time response, sensor surveillance etc at a low cost (significantly lower than sensor costs)
- It is convenient for sensor manufacturers to have a standardized software/hardware interface not having to deal with data format specifications, security, communication etc.
- If a sensor network shall be used in non-urban environments with poor or none-existing wireless infrastructures other means for data transfer (e.g. proprietary radio communication or physical, periodic data collection) must be considered
WP8
Agent based approach: The computer software structure is based on agents. In computer science, an agent is a part of the software that acts on behalf of a user or other program. The idea is that the agents activate themselves when needed and each and every task will require its specific agent. For example, a specific agent is used to calculate the probability of the presence of a bomb factory based on a measured concentration. Another one is used to combine the probabilities obtained from all sensor readings into one probable location area. The use of agents allows for a very flexible processing. Specific tasks can be added by just adding applicable agents. The agent structure allows seamless up scaling and introduction of new sensors. In EMPHASIS this flexibility has proven its added value: agents were added that allowed data from BONAS sensors to be included in the EMPHASIS processing. Additional agents made EMPHASIS sensor data available for BONAS.
Data fusion and information management: Technology development has been focused towards:
• reliable detection of bomb factory while achieving a low false alarm rate
• exact location of the bomb factory based on measurement with multiple sensors, while taking into account dispersion of gases in air (including influence of wind direction and speed)
In the EMPHASIS system many sensors used on roofs of buildings and in sewers provide a large amount of data that is fused and analysed in an innovative way. Sensor input is processed in a three stage approach (Figure 31).
The first stage is the object assessment. Based on sensor readings, clouds (either a gas cloud in the air or a solvent cloud in sewer water) are determined. Specific is the processing of scarce sensor data, measurements are not available for any point in space, for any point in time. The second stage is the situation assessment: the determination of the location of the bomb factory. The situation assessment will not directly provide one single location. Instead, it will create a source probability map, giving the probability that a bomb factory is at a given location. The third stage is asset management; the placement of sensors, their routing, the control of their scanning, their targeting, all in order to improve the effectiveness of object assessment and situation assessment, until ultimately the location of the bomb factory is fixed.
Actual implementation is using a layered approach (Figure 32). The layers are:
• Measurement
The processed sensor readings for the concentration of a given substance.
• Map
To relate all physical locations to an easy human understandable format.
• Dispersion
To calculate the likelihood of the source location, based on dispersion of the substance in air (dilution in sewer).
• Prediction
Determine the likelihood of the source location based on measurements of multiple sensors.
Each of the layers has its own agents.
Results: The current Emphasis implementation has brought sensor network based explosive detection beyond current state of the art:
• Processing of chemical sensor data, taking into account the multidimensional (2D and 3D position, 1D movement (sewage) or 3D expansion (gas cloud)).
• Application of agent based processing using artificial intelligence technology.
• Use of a sensor network while being largely independent of actual sensor locations (no need for a grid or a predefined pattern for sensor lay-out).
WP9
The feasibility study encompasses the evaluation of the possibility for applying the technical solutions from the other work packages at realistic urban conditions. The question of whether the proposed technical solution can be transformed in a business form and how the system alerts will impact the system cost has been studied.
Modeling bases have been defined to determine the context of the project. These issues were addressed separately in the sewers and in the air. Feasibility of the EMPHASIS system is really close to the environment tested. Both for sewer system and in the air, the density of population and the urban class are determinant parameters which can modify a lot the behaviour of the air system. The delivery summaries all the settings that should be taken into account to model the behaviour of the system in a specific area.
The cost effectiveness study is a benefit-cost analysis (BCA) and a decision-support tool. The methodology used for this study is based on the methodology used for industrial safety projects. The management of industrial risks raised numerous questions, which require more than ‘yes’ or ‘no’ answers:
- Which criteria should society use to decide that the level of risk of an industrial facility has been reduced as low as reasonably practicable?
- How should society arbitrate between very different criteria such as possible death and injury caused by an industrial accident, environmental impacts of industrial activity and the cost of safety mechanisms, which impact numerous stakeholders?
First, we tried to quantify directs costs (installation, maintenance and running costs of the system) and indirect costs (opportunity costs, like the loss of freedom) and also direct benefits (about the willingness to pay of the avoided damages, and the enhancement of the safety for the society …) and indirect benefits (reduction of surrounding risks).
The study of legal aspects showed that the different components of the sensors network of EMPHASIS are not subjected to the same legal issues. The sensors installed in the sewage area would probably not be challenged under the provisions of the European Convention on Human Rights. The area monitoring subsystem, which generates electromagnetic waves at a large scale, may jeopardize the right to a healthy environment as it is protected in the wake of Article 8 of the Convention. As for the mobile units subsystem, which could aim private housings' entrances or windows for instance, or even persons in the street, it could certainly be challenged under the provisions of Article 8 as causing potential interferences to privacy and to its foundation, the physical integrity and individual well-being.
However, such interferences with human rights are not inevitably unlawful, since they can be justified by proper legal provisions in accordance with the rule of law. Therefore, the operation of EMPHASIS shall be supported by a specific legal framework, for instance at national level, which would establish the conditions of an effective control of the surveillance measures and the possible judicial remedies. Finally, in some specific circumstances, the States would be entitled to set up the system for a limited period of time, even though it would breach the Convention, for instance in case of a permanent and actual risk of terrorism, materialized by bomb attacks.
Societal acceptance issues studied are the public acceptance of technologies contributing to enhance security for society and citizens but creating potential risks to public health and the operational acceptance by the various stakeholders of Improvised Explosive Device (IED) manufacturing localization.
A data collection process has been achieved in order to achieve those objectives. Studies of expert reports, European project and press on the one hand and on the other hand realization of a focus group on the other hand have been conducted.
For this study, stakeholders coming from various entities have been interviewed. During these last 6 months, an interview has been conducted with the National Coordinator Counter-Terrorism and security (NCTV) of the Ministry of Security and Justice of Netherland and a focus group has been organized with French actors. Representatives were:
- the General Secretariat of Defence and National Security (SGDSN) in the technological and prospective pole,
- Legal adviser for the General Director of the National Police (DGPN),
- Explosive section of the central laboratory of Police (LCPP) – chemical risks pole
- And the French EMPHASIS partner, INPS.
Following questions were asked to these professionals of IED prevention to launch discussions:
• Can EMPHASIS system create a social problem on privacy, confidentiality, or safety? People talked mainly about the intrusion of privacy, the public health issue, the cost for public finances and the nuisance of the technology or of the use of the operators.
• Can users reject EMPHASIS system, due to the utility, the usability or the acceptability? Discussions talked about the cost and budget rate and the staff, the necessary changes for an efficient organization to support this system, the user’s acceptability and the interoperability with other systems.
• Could the human and organisational factors variability make resilience to EMPHASIS system? Main discussions were around the evolution of the perception for actors of society and the communication strategy, the evolution of the law, the cost of organization and cost of the system maintainability, the complexity of the chain of actors (decision time), the necessity to manage data collected and the implementation of safeguards in case of false alarm and a strict policy of compensation in case of false arrest.
Then we studied the deployment options. First, significant criteria which could impact the deployment options are extracted from each previous study. Then, risks and consequences assessment methodology on projects were studied. Then, we defined three deployment scenarios for the EMPHASIS project for which we choose concrete examples:
- A system temporarily deployed on a sensible site. Example studied is the G20 summit, November 3-4 2011, Cannes, France,
- A system for a whole district monitoring in high vigilance. Example studied is La Défense business district, Paris, France.
- A system occasionally deployed for a targeted area monitoring for emergency surveys.
These examples are used to estimate the coarse costs distribution, equipment, setup and operating costs, maintenance benefit, frequency of use and lifecycle for each case. Finally, a comparative synthesis balances each cases of scenario.
Public acceptance of an innovative technology is a major issue for innovation, for security technology is even more important due to specific constraints such as the trade-off between explaining technology purpose and characteristics and making this technology effective to prevent unwanted IED-based events.
We consider different approaches. A state of art of studies and projects related to societal acceptability of innovative technology allows the identification of a set of studies the results of which can support the study of the EMPHASIS acceptance issue. Focus Group and questionnaires and an interview dedicated to EMPHASIS acceptability have been organized in order to discuss this issue with stakeholders. Finally reactions to press publications about EMPHASIS have been studied.
This study converges with results that EMPHASIS acceptance issue is complex and is a trade-off between ethical values on the one hand and the necessity of some secrecy on the other hand. This trade-off depends among other dimensions on public perception of IED–based risks, of their trust in their government, and their priorities on the use of public money. Those dimensions are variable from one country to another and may vary in time and with the occurrence of IED-based events. Definition of this trade-off will be a basis of the definition of communication strategy on EMPHASIS system and the associated development of an IED culture.
The D9.2 report estimates directs costs (installation, maintenance and running costs of the system), indirect costs (opportunity costs, like the loss of freedom) and also direct benefits (about the willingness to pay of the avoided damages, the enhancement of the safety for the society …) and indirect benefits (reduction of surrounding risks).
To conclude, the final decision for the EMPHASIS project stays a political decision and is primarily an opportunity decision that cannot be taken without a precise assessment of the current situation and, of the balance sheet of benefit-costs of each option.
WP10
The objective with this work package was to test and validate the subsystems of the EMPHASIS concept. The work ended with a demonstration of networked subsystems.
At the second project meeting in Paris, the coordinator and partners started the discussions on what should be included in the end of the project concerning the validation and demonstration of the EMPHASIS system. This resulted in a general overview on how to address this topic concerning some scenarios for improvised home-made explosive manufacturing. Moreover, it resulted in a good information to the partners on several practical issues e.g. availability to the sewage system, handling and regulations of explosive work at FOI etc. During the following project work and meeting the report on the Test plan was completed by FOI and distributed to the consortium. It was decided at the fourth project meeting that the final validation will be performed in September, 2014. The test plan for the final validation event was updated around the time of the fifth project meeting since it was decided to do a joint final validation with the EU FP7 project BONAS. This project is a parallel project to the same FP 7 call as EMPHASIS works on.
In EMPHASIS, almost all of the subsystems were validated at the end of 2013 and full completion was expected in June 2014.
The final experimental validation event has been performed in collaboration with the BONAS project. The final event was conducted on September 24-25 at the FOI test site Grindsjön 40 km south of Stockholm. The event was a two day activity with experimental contents the both of the days with emphasis on the first day.
The updated test plan was the base for the detailed practical work that was carried out between the sixth project meeting and the validation work carried out in September. The number of sensors provided from both the EMPHASIS and BONAS projects and their respective capacity needed to be taken into consideration for realising the aims of all the experimental activities.
The coordinator for EMPHASIS visited the BONAS project demonstration in Rome, Italy, in the beginning of June 2014 to further build up the knowledge about the project contents and sensors in BONAS. This was a very beneficial meeting in order to create a strong collaboration between projects and also to describe the practical possibilities and limitations that at this time could be anticipated for the joint final event. The type of compounds and scenarios was discussed on and also the timing of arrival of partners to the FOI test site in order to be prepared for the validation day. This meeting also included discussions on how to use the projects respective sensor data and how the data could be fused. The following work sorting on how to use sensor data across the project was intensified from June to September, 2014.
Subsystem testing and validation has been performed for the system communication network, the sewage monitoring and area monitoring subsystems. The experimental testings occurred at the FOI test site 40 km south of Stockholm during October 2013. Precursors to explosives in vapour phase and in the sewage were measured in realistic scenarios. The work with the area monitoring subsystems provided in-depth knowledge on how to configure/deploy sensors according to the proposed scenarios. The experimental work gave knowledge from the results that pointed to the capacity this type of system has. The sewage sensor subsystem was configured and installed in the local sewage pipes at the FOI test site. Relevant compounds were detected in the chosen scenarios and knowledge on how to make a better set-up for the validation event was acquired.
The stand-off imaging IR and Raman detection devices for traces of explosives/precursors was jointly validated in early June 2014. Personnel from Fraunhofer IAF with sensor equipment arrived at the FOI test site for joint experimental work. This work also continued the days before the final validation event in order to secure the functioning of the subsystems. Hitherto they have been extensively tested at each of the organisations labs, however, standalone from each other. Data communication of sensor data was evaluated as well in order to make sure that the EMPHASIS central system was able to receive the data. For this purpose the work on stand-off detection (WP 6) relating to the software interfaces between sensors, communication system (WP 7) and central system (WP 8) were the basis from a technical perspective.
The final validation event for the project was performed on September 24-25, 2014 (Figures 33-41). The numbers of participants were 94 with in total 13 countries including USA.
Both of the projects, BONAS and EMPHASIS, collaborated in the experimental demonstration. In addition, the previous project LOTUS was also included in the activities in terms of the inclusion of three of totally four mobile sensors. The LOTUS project concerns the mobile sensors for precursor detection mounted in roof-top boxes of vehicles.
All detection results during the demonstration were transferred to the central system and displayed. The data stored can be replayed afterwards the continuous detection and display of data. The communication with BONAS and LOTUS devices proved to be operational.
The details of the experimental demonstration are reported in classified reports of the EMPHASIS project.
Potential Impact:
Hindsight always makes solutions to problems so much clearer than at the time of their occurrence. For example, today we are aware of many risks including the high jacking of planes and their purposeful crashing into civilian buildings, with devastating effects to public well-being. But in the morning of September 11, 2001, no one would foresee that such an event was just about to happen. This was simply a failure of our imagination.
Even if we could create the perfect bomb-mitigation system, the terrorists might eventually find a way around that system. This is the foundation for dealing with the problem in multiple fronts, i.e. considering the entire terrorist timeline, from the bomb material supply chain to the detection of bomb factories and from the handling of an identified bomb-threat to the reconstruction of a crime scene. The earliest phase of them all relates to the possibility for discovering terrorists and stopping bomb attacks. This, in turn, relates to the issue: who is a terrorist and what can be done to prevent people from becoming terrorists? Today, there is no clear and widely accepted definition on terrorism, other than it apparently involves the use of violence or the threat of violence for the purpose of obtaining control, power and obtaining political goals: effective ways of releasing fear and causing destructive consequences for society and citizens globally. A significant amount of research effort has been expended on the issue of why people choose to become terrorists. Nonetheless, convincing groups and people to feel and develop destructive thoughts and terrorist actions should have a significant priority and should be a long-term preventive method.
The first known large-scale use of IEDs was during World War II and ever since IEDs have been used both for unconventional warfare in military theatres of operation such as in Iraq and Afghanistan and in terrorist attacks such as Bali (2002), Madrid (2004), London bombings (2005) and more recently in Oslo (2011) and Boston (2013). The threat of terrorist attacks is consequently a very real concern for citizens in many parts of Europe and elsewhere in the world. IEDs can be manufactured from military and commercially based explosives or home-made explosives and often a combination of these are used in terrorist attacks. Fundamentally, terrorists use whatever is easily available for the preparation of bombs and due to the wide range of options in this respect there are numerous parts that comprise the threat to the society.
The Bali bombs, 2002, were manufactured in a two-story house a few kilometres away from the terrorist attacks resulting in hundreds of dead and injured people. The bomb factory had not been disturbed since the bomb makers departed and forensic experts could make a vast amount of analyses. The bombs were found to be based on a combination of potassium chlorate and aluminium powder.
Both of the substances used in the Bali bombs are non-volatile and unrealistic to find in air, however, it is likely that these can be detected as traces in the vicinity of bomb factories or in the waste water pipes originating from such facilities.
In March of 2004 in Madrid, ten bombs against the commuter train system exploded due to a coordinated terrorist attack resulting in hundreds of killed and injured people. Shortly after the attacks the police identified an apartment in Leganés in south of Madrid as the likely bomb factory. The suspected people trapped in the apartment set-off their explosives resulting in killing themselves, nevertheless, investigators later found out that the explosives used by the suspects were of the same type as those ten bombs used on 11 March. The bombs were found to be made of Dynamite probably bought from a retired miner who still had access to blasting equipment.
Also for this terror attack an apartment was used as an IED manufacturing facility in an area with a large number of inhabitants.
It is evident that there exists an urgent need for new tools in the extensive work of preventing future terrorist attacks and this is a large scientific challenge in the security domain today for the development of systems for preventing the manufacturing of home-made explosives (HMEs) and stopping bomb attacks at an early stage. For the law enforcement services there is a large need for tools that contributes to the early discovery of bomb attacks at specifically the planning stage.
The preparation of an IED involves different phases, where planning and financing the operation is the first phase. Thereafter precursors are obtained either illegally or purchased legally and transported to the location where the preparation of the IED is performed. The phase before execution of the operation takes place in a so-called bomb factory, for example a kitchen or a garage, where equipment and chemicals are manipulated in order to create the IED. The discovery of bomb factories is of primary importance in the prevention of terrorist activities, where investigations can be conducted with fewer time constraints and with greater accuracy than in later stages. The detection of precursors complies with the “Early warning system concerning explosives”, which is “Priority 1” of the “Prevention measures” in the Action Plan on Enhancing the Security of Explosives. Recently the European Commission has released a regulation on the precursors available on the market.
Due to the large variety of HMEs that can be prepared, currently there are no specific commercially available sensors to survey the presence of precursors or the transformation of such chemical compounds into IEDs inside a suspected environment. The search, monitoring and identification of suspicious substances are also complicated by their different physical properties that they possess (vapour, solid, liquid). Specific EU FP 7 Security Projects have addressed this task (LOTUS, BONAS and presently EMPHASIS), considering strategies to put in place, giving priority to some precursors to be detected and supporting the development of specific sensors. The use of different sensors is not a unique answer to the detection of the threat but is a part of the toolbox needed to identify the suspicious factory.
A timeline for the terrorist preparations include several steps. In the planning and financing phase, terrorist plots may mainly be revealed through conventional intelligence gathering methods, e.g. surveillance of known terrorist groups, informants, monitoring of money transfers or intercepting the group in a robbery. In many cases, necessary household chemicals or chemicals readily available in hobby stores can be obtained at low cost and little effort. Monitoring trade of restricted materials may be one possible way to reveal terrorist plots at this stage if large amounts of material are purchased or stolen.
The preparation and production phase can by necessity be quite long (weeks to months). Unless the bomb-makers are quite professional they will need to test and practice the procedures and in many cases the chemical manufacturing process in itself takes considerable time. An example of the production time frame is the London attacks. The terrorists obtained hydrogen peroxide, one of the main bomb ingredients. “They could buy it as liquid in an 18 per cent concentration. Between the end of April and July 5, 2005, they are alleged to have bought 443 litres in either one-litre or four-litre containers.” They then reduced it to higher concentration in their kitchen.
Detection in the production phase has several distinct advantages compared to detection in the transportation phase. There is more time available for detection, some detected substances may be present in larger quantities, if a threat is detected, there is time to take further actions. During the production of explosives and even drugs or CWA, elevated amounts of precursors can normally be present in the air. Evidence of this is found in the reports by residents in the neighborhood around the Leeds “bomb factory” where the explosives for the London bombs of July 2005 were made. The bomb makers bought hydrogen peroxide in 18% concentration and “three members of the gang are said to have spent long hours sweating over the electric cooker in the small kitchen, boiling huge panfuls of liquid hydrogen peroxide to reduce the chemical into a stronger concentration.”
Regarding the smell, local resident John Langlan said:
“I think it was that strong around this area that it affected and killed all the plants and they have just started growing back now - that is how long it has taken”.
Detection during transportation is much more disadvantageous than detection during production. First of all, the detection itself is more difficult and the time frame for intervention activities is also much less as compared to the production phase. Furthermore, even in case of successful detection in the transportation phase, the interruption of the attack is not without risk. If the person carrying the bomb is a suicide bomber, the bomb may be detonated with severe consequences for law enforcement personnel as well as innocent bystanders. Detection during the production phase gives more time for law enforcement to act without risk for themselves or others. When the plot has reached the last phase - the attack itself - it will be too late and severe damages and casualties will be a fact.
The outcome from a system such as EMPHASIS would be to narrow down the search area of the illicit production to a couple of blocks or even pin-point the bomb factory. The data produced from a system such as EMPHASIS should be seen as intelligence information that needs to be complemented with other intelligence before any intervention activities are initiated. Furthermore, the EMPHASIS system would make it more difficult for terrorist to prepare HMEs without being discovered. The main benefit for finding bomb-factories would be the capacity to stop a devastating bomb-attack at an early stage with minimum consequences for society and citizens.
The virtue of the technology for the EMPHASIS central System is the ability to create awareness of a complex 3D environment using a network of randomly dispersed heterogeneous sensors. The awareness is highly reliable, on one hand by the low false alarm rate, on the other hand by its low “missed hit” rate. Due to the heterogeneous sensor set, it is virtually impossible to hide for the sensor suite.
Hereby the technology adds to the impact of the EMPHASIS system. In addition, a predecessor of the technology proved its value during the successful demonstration of the (EDA) ICAR project. Both projects have in common they act upon terrorist-like activities, work in a complex 3D environment and are searching for activities that the terrorists like to keep hidden.
Potential impact of the technology can be in the area of:
• Counteracting terrorism
o Countering bomb production (EMPHASIS)
o Denying the use of the RF environment (ICAR)
o Detection and tracking of Piracy activities
o Etc…
• Awareness in complex environments:
o Search and rescue
o Sea and land border patrol
- Countering illegal immigration
- Countering drug smuggling
- Etc…
o Surveillance
- Set a watch on complex extended objects like airports
- Etc…
o Monitoring of large infrastructures
- Pipelines
- Production plants
- Etc…
o Countering drug production
- Detection of drug production sites
The security industry is complicated by the need to balance the security of people with respect to the extent of preventive actions. After the 9/11 attack in 2001, Europe has experienced tragic attacks by terrorists (Madrid 2004, London 2005, and Oslo 2011) to mention a few involving the use of homemade bombs. An important question that follows concerns the amount of funds to be allocated to ensure the safety of the European citizens, and the world at large. During the course of the seventh framework programme, the European Union has invested a large amount of money in order to boost the relatively new and complicated research area called “Security of Explosives”. It is complicated in the sense that terrorists must not know what the possible counter measures are. This is one very important fact that makes classification of information necessary within this area. A cost-effectiveness study has been carried out in the project with focus on the EMPHASIS system where parameters such as e.g. equipment and staff training costs, installation and lifetime of components have been considered. The possible deployment of the EMPHASIS tools has been studied taking into account a few different scenarios in an urban environment. Furthermore, the public acceptance and legal framework has also been evaluated for the view of understanding how a system such as EMPHASIS can be used as a future security measure.
The development efforts made in the project have been communicated in several ways during the project. EMPHASIS information has been distributed via the EMPHASIS public website, by the participation in public media such as BBC world, radio and TV, in Swedish public media and in a number of newspapers and websites, e.g. New Scientist, Foxbusiness, CBS news and Dailymail and by taking part in scientific conferences. Furthermore, in the project a number of written reports with various dissemination levels (classified and public) have described the research progress continuously during the project.
Going back to the call ”Improving the security of the citizens” there is no doubt that the EMPHASIS system has the potential to improve the security of citizens. The project has shown that it is possible to locate illicit production of certain chemicals, within a sufficient timeframe. There are several ways of operating the EMPHASIS system. It may be used as a continuously monitoring system or as a reactive system used when suspicions, or needs, arise. The central server and client computer may easily be integrated into existing control/supervision centers and the communication channels are already in place.
The short-term potential impact depends on some factors; building sensors for daily use without costly maintenance, ensuring that the substance(s) detected matches the substance(s) of interest and a pronounced demand from one or several end-user.
In the long-term the EMPHASIS system has a large potential. Since the infrastructure needed is in place in most countries the main factor driving widespread use relates to the cost, performance and deployment of the sensors.
Sensor deployment depend mainly on size and power consumption, both of these factors are driven by technology development and volume production. Already today some of the components constituting the sensors are off-the shelf products. Within some years of technology development a sensor may be even more compact and possibly within a ten-year period it could be foreseeable that a sensor may be a medium-cost unit. Performance-wise, the sensors will benefit from the current miniaturization of electronics and optoelectronics which can enable enhanced detection of multiple substances in one single sensor as well as increased sensing performance.
No doubt, the potential applications of the EMPHASIS system will increase when sensors may be deployed in large numbers and can detect a multitude of substances. These applications will not only include localization of illicit manufacturing of different chemicals, but also detection of environmental hazards and long-term environmental monitoring. The system may also serve to generate statistics of chemicals present in the environment and generate data for the research community. As with many other systems, applications will pop-up once the capability is in place.
From a security perspective a geographically distributed EMPHASIS system may also aid and facilitate cooperation between nations in security and anti-terrorist matters. The various uses of the system may also facilitate cost-sharing between different end-users.
In summary, the performance and the successful use of a system such as EMPHASIS depends mainly on the type of sensors used in the system. It is the detection performance that is the most critical factor if a threat substance can be detected or not. If the needed detection capability exists then other factors will also influence the final result.
For detection in the vapor phase, the IR spectroscopic subsystem is at a level where it can be foreseen to be used in a real scenario for certain chemicals since it has the required sensitivity, selectivity, speed of detection and size of subsystem components. For the Raman spectroscopic subsystem, it has from the view of using the Raman based principle potential in the future for use in a system of the EMPHASIS type in terms of sensitivity and selectivity, however, much more technology development are needed for different components of the system in order to realize a dimensionally smaller system with also better sensitivity, ease of use and cost effectiveness.
The ion selective electrodes used in the project have been valuable in the research and have enabled to prove the viable concept of EMPHASIS for the detection of precursors in sewage. The sensor technique as such needs however to be developed much further in order to enhance parameters such as sensitivity and selectivity of the technique. This is required in order to realize these types of sensors in a system of the EMPHASIS type. Probably, other sensor techniques based on other detection principles will be of larger interest in the long term perspective.
For the detection of traces of explosives or precursors on different surfaces, both the IR and Raman based techniques are considered as having adequate sensitivities and selectivity’s. It will be of advantage in the further development work to enhance specifically the sensitivity but also the range of compounds that can be detected. In terms of cost effectiveness, the components building up the subsystems will hopefully be smaller and less expensive and this will be of importance for end users if commercialization of the tools is considered. The advances in the field of optical components are generally progressing fast and the future outcome will be of importance to follow from an explosive detection point of view.
If an EMPHASIS system had been existing 2005 and had been put into operation before the London bombings, the Leeds bomb factory might have been discovered. Consequently, this would have offered police forces the possibility to intervene and catch the terrorists at an early stage of the terrorist activities. This would then have stopped the attack and many lives would have been saved.
Detection of explosives has traditionally been focused at the stage when an explosive charge is already ready for use, being transported to or already at the scene of an attack. Preventing terrorist attacks while they are already in motion is extremely difficult. Not only is it difficult to find an explosive on a person or in a bag but one must also face the need to do this in a very short time for countering the attack once a possible suspect or suspicious object has been found. The capability to intervene at an earlier stage is therefore of very high importance. In the preparation phase it is mainly detection of the production that can be carried out. Detection of high vapor pressure explosives themselves could be of importance, but it is more likely that some of the best candidates for detection are the precursors used to make the explosive and possibly also by-products from chemical synthesis that could escape (to air, drains or sewers) during the production process. Basic issues like what substances to look for and where to best look for them are as important as how to look for them. Detection in the preparation phase has several distinct advantages as compared to detection in the phases where an attack is in motion. For example, there is more time available for detection, some detected substances may be present in larger quantities and if a threat is detected, there is time to take further action.
The overall objective with the EMPHASIS project was to test a system concept for detecting ongoing illicit production of explosives and improvised explosive devices (IEDs) in urban areas. The EMPHASIS system is composed of different sensors in a network. Area detectors, strategically positioned, for the monitoring of explosives or precursors to explosives in the vapor phase are used. Multiple static sensors, positioned in the sewer, for the monitoring of the sewage for indicative traces are also used. The detectors are connected in a network and the total gathered data is fused and evaluated in a command center. If a threat substance is detected in elevated amounts, information about the type, location, time and amount is registered and sent to a command center where further evaluation and appropriate actions is performed. The intention is first to cover a large area that will be reduced step by step to smaller areas. The exact pinpointing of the bomb factory is performed using stand-off detectors that can be transported in mobile equipped units.
The sensors and data system protocols have been validated in the field of the test site at the Swedish Defence Research Agency premises. This has been a most valuable procedure in order to be able to match interfaces with the techniques used. The final experimental demonstration has been performed together with BONAS, a parallel project within EU FP 7. This final event gathered 94 participants from 13 countries including USA. The demonstration showed 15 sensors that were used for precursor/explosive trace detection in relevant scenarios. The central system of the EMPHASIS project could read in sensor data from all the sensors (EMPHASIS and BONAS) and display these on a map relating to where the detection occurred together with other data such as concentrations and time for detection. The compounds detected were emitted from sources in relevant scenarios developed within the EMPHASIS project and deployed in a secure and controlled manner at the closed test site. It can be concluded that the concept of the EMPHASIS system is a viable approach for certain scenarios and that the basic capacity of some specific detection techniques are considered as sufficient. Nevertheless, still there is much room for future technical development work in this field where also other types of detection technologies could be of interest to incorporate into a system of the EMPHASIS type.
Project Context and Objectives:
The discovery of hidden bomb factories is of primary importance in the prevention of terrorist activities. In particular, the first stages of manufacturing of improvised explosive devices (IEDs) can take more time as compared to the successive phases comprising the transport to the target of the IED and execution of the attack. In the early stages of IED preparations for a terrorist attack, investigations can be conducted with fewer time constraints and with greater accuracy than at later stages.
One key aspect in the fight against terror actions with homemade explosives is to prevent the use of ordinary chemicals from being used as precursors to explosives. Home-made explosives (HMEs) are easy to make from readily available materials used for legitimate purposes in everyday life. This availability attracts terrorists and criminals to manufacture and use HMEs since military and commercial explosives are more difficult to come by. The uncontrolled information disseminated via the web and the simultaneous presence of trained persons enables large populations to prepare and build IEDs containing Improvised Explosives (IE). IEs can be realized at home using products that can be bought without any specific authorization (e.g. ammonium nitrate and other chemical substances) and using simple equipment present in ordinary kitchens.
The manufacturing of home-made explosives requires work with starting chemicals that needs to be processed into the right products for the assembly of explosives and bombs. The work could lead to the release of vapours and aerosols to the outdoor air of the clandestine laboratory where wind and urban turbulence will dilute and disperse the traces in the surroundings. Equally as important is the detection of target compounds in the sewage where detection is possible due to that cleaning of production equipment might have been performed.
In order to locate a bomb factory it is necessary to work with a variety of sensors able to detect vapours and aerosols, solid traces of explosives on various objects and compounds that might be flushed into the sewer. The project EMPHASIS has worked with the tasks concerned by developing system prototypes and thus being able to show proof of a principle for this new capability. The monitoring of large areas using a network of sensors with varying capabilities generates a large amount of data that are transmitted via wireless networks to remote computers. At this command central, the type/concentrations of target compounds and position/time for the detection of target compounds are displayed on a map. The compiled data could benefit the decisions of end users in case of a positive alert and advantageously complement to other intelligence that might be at hand.
One of the largest scientific, technological and deployment challenges in the security domain today is the development of systems for localisation of IED manufacturing facilities or prevention of the use or enhanced detection possibilities of commercially available precursor chemicals. The IEDs, that can be prepared in ordinary kitchens, contain explosives that in terrorist attacks give devastating effects. For the law enforcement services there is at present an urgent need for tools that contributes to the early discovery and neutralisation of illicit production of explosives. The most important and concrete contributions from systems such as EMPHASIS with respect to the complex task of locating IED manufacturing facilities or hindering production of home-made explosives are:
• An early warning
• Pinpointing of the location of the bomb factory
• Automatic system
• Less personnel requirements as compared to normal intelligence
• Enhanced HME detection capability
Detection during the production phase gives more time for law enforcement to act without risk for themselves or others.
The mechanisms for the dispersion of explosives or precursors to explosives to the surrounding environment will be different depending on if explosives or IEDs are manufactured. If the explosive must be produced by chemical synthesis from some type of starting substances (solvents and reagents) there is probably a larger chance for emission to the air. The volatility of a compound, reflected by its vapour pressure, is an important factor that influences how much of the compound that will be distributed to the vapour phase. In order to have a manageable working environment in the bomb factory a proper ventilation of the room might be necessary. This could be achieved using kitchen fans and open windows. The ventilation of the room will give dispersion of the explosive vapours to the outdoor environment. For the terrorist attacks in Bali (2002), the bombs used were manufactured by mixing chlorate and aluminium powder. These substances cannot be found in the gaseous phase due to their chemical properties. However, small particles originating from these substances can likely be present in the surrounding environment of the bomb factory. The particles can be transferred and adsorbed to surfaces such as door handles and banisters. Chlorate ions will be present in the sewage if e.g. cleaning of equipment has been performed in the illicit production of these IEDs.
In summary, explosives and precursors to explosives can be emitted via several pathways e.g. via the exhaust of the ventilation system, as well as windows and chimneys and close to these emission points the deposition of the exhaust can lead to a surface coverage of traces. In addition, because of transportation, unpacking and handling of the chemicals, the ground in the vicinity of door and car entries and door-handles at the entries of the location can be covered with traces of precursors/explosives. Furthermore, during the illicit production, traces of precursors and by-products needed for manufacturing of an IED can be present in the sewage from the building.
In EMPHASIS, the focus for the detection is on three types of cases; Detection of explosives/precursors in vapour phase at low concentrations; Detection of explosives/precursors at low concentrations in sewage; Detection of particles (low concentrations) e.g. door-handles or other covered surface. The fusion of sensor data leads to potential alerts.
A key aspect of the EMHPASIS concept is that it can allow efficient intelligence lead assessment of an area of a city in order to establish where, and more crucially when illicit bomb-making activity is occurring. A system based on EMPHASIS can lead to a very significant reduction in surveillance man-power of suspect areas. Critically, when a narrow area or house has been identified as being under suspicion, the system can provide invaluable assistance in the timing of police intervention increasing the chance of successful convictions as a consequence.
The sensors in the EMPHASIS system are capable of detecting explosives at extremely low concentration levels (ppb for vapor detection) where totally five different sensor types have been used; two sensors for the air-monitoring subsystem, one sensor type for the sewage monitoring subsystem and two sensors for the stand-off detection of particle traces.
The air-monitoring subsystem in EMHPASIS is based on the combination of two spectroscopic methods which are resonant Raman scattering and Infra-Red (IR) absorbance. Both methods are based on irradiation of a sample with monochromatic radiation from a laser. The collected and analysed radiation will result in a compound specific spectrum. The advantages with the sensors are that they will be able to monitor very long distances, hundreds of metres, and determine the distance to the target compounds and also the concentration of the compounds at this position.
The homemade bombs manufactured by terrorists often contain compounds such as chlorate, perchlorate, ammonia, nitrate, and hydrogen peroxide. Most of these compounds will be present as ions when dissolved in water (sewage) leading to changes of the pH and the conductivity of the water. These properties can be analysed using ion selective electrodes (ISEs). An ISE is a sensor which converts the activity of a specific ion dissolved in a solution into an electrical potential which can be measured by a voltmeter or pH meter. In EMPHASIS, a bunch of ISEs with different selectivity’s in order to facilitate the detection of a variety of compounds have been used. The detection performance for ISEs is in this project adequate for checking if the concept is viable for detection of precursors to explosives in sewage. It should be regarded as a research tool to understand and verify a proof of principle. Ion selective electrodes have generally a detection limit at the level of mmol/l or lower. In laboratory use, with extensive sample preparation, the limits can be reduced to mol/l levels; however, considering the deployment of sensors in a very contaminated matrix such as sewage these limits cannot be achieved.
The sensors for imaging stand-off detection will enable the detection of particulate traces of explosives and precursors on surfaces such as door handles, mail boxes, exhaust openings or chimneys. The basic principle of the infrared backscattering laser spectroscopy is that organic molecules such as the substances of interest absorb radiation in the infrared spectral region. The objects under investigation in the project were illuminated with laser radiation and the diffusely backscattered radiation was collected and analysed using multivariate analysis. The imaging Raman technique used the same analysis principle, however here the Raman scattered light is detected. The techniques can work in parallel and the fusion of the data from both techniques can reduce false alerts.
The terrorist attack executed on the London Underground July 2005 is a horrible example of the result from the manufacture of home-made explosives. The manufacturing of the bombs for the London Underground were performed in the neighbourhood of Leeds. In contrast to the bombs used on July 7 resulting in many victims and injured people, the bombs used on July 21 all failed giving much material for forensic analyses. The bombs were based on a home-made peroxide system where ordinary commercially available chemicals were bought and further modified in a normal kitchen. Many starting chemicals used for making home-made explosives are volatile. Volatile chemicals are possible to detect in the gaseous phase and could be emitted through open windows and kitchen fan systems. The dispersion to the surrounding air is a function of parameters such as weather conditions and city architecture.
The EMPHASIS project started 2011 and ended technically by the demonstration in September 2014. The EMPHASIS system should be regarded as a technical tool for intelligence gathering, rather than a detection system, meaning that the information obtained should be combined and confirmed with information from other sources to make the most accurate assessment of the situation. EMPHASIS is a project where a system concept was developed and tested.
If an EMPHASIS system had been existing 2005 and had been put into operation before the London bombings, the Leeds bomb factory might have been discovered. Consequently, this would have offered police forces the possibility to intervene and catch the terrorists at an early stage of the terrorist activities. This would then have stopped the attack and many lives would have been saved.
Project Results:
WP2
The objective of WP 2 is to disseminate the results and findings of the EMPHASIS project to the partners, to interested Stakeholders, including end-users, the European Commission, Governments, legislative and inspection bodies, law enforcement agencies and the public. It is also to ensure a market for the EMPHASIS system that is useful and applicable for the end-users.
A public website has been set-up and delivered Month 4 in the project. The website will continuously be updated during the project. All the public deliverables will be available for download via this website. www.emphasis-fp7.eu.
WP3
The objectives for WP3 were to define user requirements, identify the threat substances including a characterization of these threat substances in the environment in which they will have to be detected/monitored, as well as setting up realistic scenarios and a detection strategy for deployment of the EMPHASIS concept.
Based on interactions with potential end users, feedback was received on the end user requirements for the tools to be developed within the EMPHASIS programme. These tools comprise air, sewage and trace monitoring of home-made explosives (HMEs) and precursors needed to illicitly prepare HMEs. In the beginning these end user requirements could not immediately be translated to technical specifications, but later on in the project and after continued contacts with end users during Workshops, this translation could be made.
An update of the threat substance list resulting from the EU FP7 LOTUS program was made and a selection of relatively new threat substances was synthesized and characterized. This resulted in validated data on (internet) recipes and some physical and chemical properties of these threat substances. This also included precursors required for the synthesis of the homemade explosives. Furthermore, simulations with CFD (computational fluid dynamics) were performed and realistic velocities of flow, concentrations, dispersion and expansion of threat substances in sewage could be determined. Because of the huge variety of influencing parameters within sewer channel systems (e.g. flow velocity and filling level), CFD calculations were performed for one model substance spreading in two characteristic discharge cases.
Several terrorist attacks that occurred in the past in the EU (Leeds/London, 2005; Stockholm, 2010; Oslo, 2011) were described in detail, including the timeline going from preparations, procurement of ingredients, manufacturing, transport to the target and the final attack. These attacks formed the basis for deriving realistic scenarios that were used to verify and optimize the different detection techniques under development within EMPHASIS (area monitoring, sewer monitoring and stand-off trace detection). On the basis of interviews with end users, a compilation was prepared of current search strategies and an analysis how the EMPHASIS tools could further contribute to the intelligence and technical support tools that are available today to end users and law enforcement agencies.
WP4
The objective of WP4 was to define target substances in sewage and to build and test a sensor node including detection limits, fouling behaviour, data analysis and integration into the EMPHASIS information network.
In collaboration with WP3 target substances for sewage water have been selected. All substances must be of interest regarding both their usefulness for illicit production of explosives as well as their basic properties making them compatible with sewage water.
The sensor node itself comprised ion-selective electrodes (ISE) as a detection unit.
ISEs from different manufacturers have been selected and were first characterized in de-ionised water to determine their sensitivity towards the chosen threat and benign materials. After successful results, these measurements were repeated in tap water and artificial sewage water according to a recipe from the German Institute of Standardization (DIN). The influence of background matrix composition was evaluated and used to develop models to compensate drifts within the sewage composition.
Concepts for hardening the sensor for sewer water application were developed by investigating the influence of a long-term immersion within standing artificial sewage water to fully enable fouling processes. The response characteristic of the sensor node was recorded before and after a four week immersion time. While fouling products were present alongside with large contamination of the sensing membrane of the electrodes, response characteristics did not change over time. From these experiments an automated cleaning procedure once a week was advised.
In order to determine the probable concentrations of explosives or their precursors, CFD calculations as already mentioned in WP3, helped to understand basic principles of concentration ranges within sewer systems as a function of the distance to the insertion point and the starting concentration and overall amount. These simulations made it possible to assess the performance of the different electrodes and the boundary conditions for the real-world tests.
With these data a model sewage was constructed and the characteristic responses of the electrodes in flowing water were recorded. Detection limits for different substances in constant flow and cross-interferences to benign substances were re-evaluated. The response time of the sensor was compared to the background flow provided by normal sewer systems to ensure compatibility between the sensor and real-world application. Experiments showed that the system was able to cope with different background matrices even such different ones as tap water and artificial sewage. The CFD simulations allowed an estimation at which distance from the insertion point a sensor could reliably detect a given amount of target substance.
Finally, the data acquisition chain was developed. Since COTS electrodes and their respective read-out devices are not meant to work as a multi-electrode sensor system, fusing all data from the different sources into one data file had to be performed. This was done by using serial printing from the read-out devices and redirecting the data into different files. These files were processed to extract and merge to obtain files ready for subsequent data processing. Using several different software solutions (from recording to manipulating and analysing under both Microsoft Windows and Linux on one system) it was possible to develop a solution. Data processing was done by using OriginLabs, Origin including realtime import, automated multi-peak picking and evaluation as well as pattern recognition. The results were then post-processed to fit the requirements of the EMPHASIS router.
The last step in the project was a demonstration at FOI test site in Grindsjön, Sweden. The system was installed in a real world sewer system running autonomously. Environmental conditions were rain and heavy wind, so rain water and organic material such as leaves were brought into the sewer system. Nevertheless the system was able to detect, identify and quantify threat substances while not registering benign substances. It could also be shown that the background matrix (tap water or artificial sewage water) had no influence on the detection performance. The sensor itself was fully integrated into the EMHASIS network and used the set-up router system to send its data to the central system.
WP5
Between month 1 and month 24, Cascade has completed the build, assembly, test and demonstration of 3 Infrared Air Monitoring prototypes based on CT3000 OEM core engine. The various measurement campaigns have been a success and the system prepared and sent for field test and validation at FOI Grindsjön site Sweden.
The final system capability is in terms of the compounds to be detected is listed in a classified report and also as function of available laser wavelengths.
Initial detection was tested in a closed long path configuration to assess limit of detection (LoD) in ppb.m for certain compound of interest. Limit of detection currently ranges between 300ppb.m to <100ppb.m. Open path LoD tested in function of plume size. The measurements obtained at FOI Grindsjön site have been reported in a classified report.
Between month 25 and month 36 the EMPHASIS Infrared Air Monitoring systems have been finalised for the demonstration. The setup was composed of 3 identical Infrared Air Monitoring units in an open path arrangement in a network covering an area. Each system had an open path capability of up to 400m which render them ideal to be strategically positioned covertly on roof top of buildings for the monitoring of explosives or precursors to explosives in the vapour phase during illicit manufacturing.
The system was successfully tested at FOI site, Grindsjön, in October 2013, May 2014 and September 2014. This led to a successful end of project demonstration at the end of September 2014.
The Infrared Air Monitoring system sensors are the first QCL based systems capable of fingerprinting (detecting) and monitoring the concentration down to part per billion (ppb) levels in real time (2Hz detection rate) of several compounds of interest simultaneously. To date, the EMPHASIS works relating to the Infrared Air Monitoring system has resulted in the characterisation, fingerprinting and test of 4 target compounds linked to the illicit manufacturing of improvised explosive devices (IED).
During the demonstration, the Infrared Air Monitoring system was capable of detecting precursors in vapour phase leaking out from the ventilation of a cabin with a kitchen inside (i.e. replicating illicit manufacturing of IED). In the Infrared Air Monitoring system each sensor is based on rapidly chirped quantum cascade lasers operating in atmospheric micro-windows and advanced infra-red detector technology.
During the final demonstration the successful detection of 4 compounds was demonstrated under inclement weather conditions using three Infrared Air Monitoring Systems. Compounds were detected on different beam paths, demonstrating that a network of Open Path Analysers could be successfully used in an urban environment in order to identify likely locations of illicit IED manufacturing activity. When combined with other technologies such as mobile sensors and sewer monitoring, the ability to home in on a threat becomes increases.
Optical system configuration:
Air monitoring subsystem 1 operates in an open path optical configuration of several 100 meter length with signal backscattered from retro reflectors. Cascade and Vigo System S.A. have used optical modelling in ZEMAX software to validate the design.
In order to meet system requirements for accurate beam positioning a variety of different types of detectors have been suggested. Vigo System S.A. considered both flat and immersed detectors in quadrant configuration. The advantage of flat detector array is its high fill factor- having no insensitive gaps it is possible to position small beam spot very accurately. However, flat detectors features too low sensitivity and they are not feasible in this project. The back reflected power reaching the detector is too low to be detectable by flat detector. Therefore, compositions incorporating immersion lens has been considered. Application of a hyperhemispherical lens configuration makes the incoming radiation to increase detector capability by an order of magnitude.
For beam positioning applications there were two solutions with immersion lens considered. The first approach was to assemble four single element detectors with immersion lenses on a sapphire carrier in a quadrant arrangement (Figure 1). The quadrant constitutes the single element optical area. It can be noticed that there are huge spaces between neighbouring detectors. Due to large insensitive gaps this solution was rejected from further analysis.
The second solution utilized four detectors with one immersion lens (Figure 2). This solution has been considered as the most promising one, as featured both, high sensitivity due to application of immersion lens and high fill factor as the 4 elements were very close to each other.
Detector system adaptation:
The UK SME Cascade was working with the Polish SME Vigo System S.A. in order to decrease the current detector noise level and improve the signal to noise ratio and beam pointing stability. The dedicated IR detector was optimized for the specific needs of the Emphasis project (air monitoring subsystem).
The device was integrated in a compact detection module that consists of:
- detector element
- ZnSe window with AR coating
- preamplifier
- Peltier cooler
- cooler controller
The key features of the detector are listed below:
- system returned power has been modelled at 0.1% (0.5mW from 500mW peak)
- the detector technology is based on MCT photoconductive detector (PCQI) in a quadrant arrangement of 4x(1x1 mm) or single element photodiode (PVI)
- the detector is stabilised in temperature by a 3 or 4 stage Peltier element
- immersed optics increase responses
Vigo System S.A. has manufactured few detection module prototypes according to detector system specification and resulting from ZEMAX optical modelling. Both photoconductors and photodiodes were developed because it was not clear which type would be the best one. Photoconductors are mature and reliable devices that can have large active area but they are vulnerable to saturation. Photodiodes offer potentially better performance but long wavelength photodiodes are frequently limited by the tunnel and parasitic impedances. They also show significant 1/f noise in the required frequency range and their active area is limited. The limitations are of technological rather than fundamental nature and can be overcome with device design, growth and processing refinements.
The first detector prototype takes the form of a quadrant detector arrays (photoconductors) to allow active X/Y steering of the TX/RX optics with respect to the retro reflectors insuring constant alignment and optimum signal strength. The second one was based on single element photovoltaic device.
Detector concept:
Implementation of dedicated detector for the air monitoring subsystem system is based on the concept of IR photodetector developed at Vigo System S.A (Figure 3). that relies on integration of optical, detection and electronic function in a monolithic heterostructure chip. The functions are:
- concentration of radiation
- enhanced absorption
- efficient and fast collection
- suppression of thermal generation
- internal photoelectric gain
The basic detector material is HgCdTe graded gap alloy, characterized by outstanding photoelectric and structural properties. Since lattice constant is weakly dependent on composition, the material can be used for complex 3D chips whose regions serve as radiation absorber, minority and majority carrier contacts, optical concentrator, passivation and other purposes.
Manufacturing process:
Emphasis detectors are produced from HgCdTe (MCT) grown by MOCVD AIX-200 epitaxial system for II-VI compounds on GaAs substrate (Figure 4). CdTe buffer is grown on GaAs to reduce strain due to lattice mismatch. Growth is fairly well reproducible in short time frame, its need to be fine-tuned for long term reproducibility. Material is measured, and after acceptance may then be processed into planar photoconductor or MESA-structured photovoltaic detectors. After that, passivation (CdTe) and metallization (Cr-Au) layers are deposited. Wafer is diced with a diamond saw and dies are measured and accepted for immersion lens micropolishing. Active element centring, lens shape and size are controlled. Measured lenses are flip-chip bonded to sapphire chip carrier, then glued to four stages TE cooler and assembled in TO-8 based package. Chip carrier is wire bonded to TO-8 package leads. Desiccant is placed inside the package, device supplied with ZnSe window and backfilled with an inert gas.
Detectors are measured using FTIR spectrometer, blackbody, impedance analyser and I-V characterization tools.
MOCVD growth:
Epitaxial growth of heterostructures for Emphasis detectors has been carried out in the AIX-200 II-VI MOCVD system equipped with gas foil rotation for better composition uniformity (Figure 5). The reactor which consist from a horizontal rectangular duct quartz reactor cell (liner) is enclosed in an outer circular quartz tube. Two separated gas inlet channels are provided to prevent premature gas reactions and dust formation. Hydrogen is used as a carrier gas. Dimethylcadmium (DMCd) and diisopropyltelluride (DIPTe) used as precursors are held in temperature-stabilized baths. Ethyl iodine (EI) is used as a donor and tris-dimethyloaminoarsenic (TDMAAs) as acceptor dopant source. DMCd and EI are delivered through the upper channel while DIPTe and TDMAAs are delivered through the lower channel over the quartz container where elementary mercury is held. The wafer holder was made of SiC coated graphite capable of holding up to two inch diameter substrate. The substrate, GaAs (100)2°→(110) was heated with halogen heaters situated directly underneath the wafer holder.
Hg1–xCdxTe and CdTe layers are grown at ~350ºC with mercury source kept at 210ºC. Typical pressure in reactor during deposition is 500 mbar.
Direct Hg1–xCdxTe growth is difficult due to very different thermodynamic properties of HgTe and CdTe. We applied interdiffused multilayer process (IMP) for Hg1–xCdxTe growth to avoid this problem. IMP gives controllable growth of heterostructures with complex composition and doping profiles. In IMP growth, HgTe and CdTe layers are deposited one after another with period 100–200 nm and homogenized by interdiffusion during growth. Any composition can be achieved this way by proper selection of HgTe and CdTe layer growth times.
HgCdTe structures for Emphasis devices are deposited on GaAs substrates. Time of growth vary from 5 hours to ~12 hours in dependence on the detector type.
Growth begins with CdTe buffer deposition to accommodate lattice mismatch and isolate from unintentional doping from substrate/surface. Buffer is followed by HgCdTe structure having both relatively uniform and graded (gap and doping level) regions. The graded gap regions are obtained by programmed growth.
The practical issue in implementation of the Emphasis devices with MOCVD is significant interface grading caused by Cd/Hg and dopants diffusion at the growth temperature. The diffusion allows using IMP technique, but at the same time prevents from obtaining steep composition and doping profiles. Precise composition and doping shaping requires knowledge of nonlinear Cd, Hg, I and As diffusion parameters in HgCdTe. Unfortunately, the parameters vary with composition, time, dopant concentrations and dislocation density. In practice, growth parameters must be determined in series of growths experiments. The SIMS profiles are invaluable in revealing differences between planned and practical heterostructures.
Characterization of grown structures involves transmittance and reflectance spectroscopy, Hall measurements, thickness from cleavage, SIMS and photoresponse spectroscopy and other techniques.
Dozens of photoconductive and photovoltaic HgCdTe structures were deposited for the detectors in this project with purpose to implement required composition and doping profiles designed by computer simulations.
Mechanical design:
The mechanical design of the detector is based on commercially available TO-8 sub-mounts with soldered miniaturised thermoelectric coolers. Peltier thermoelectric cooler (TEC) is a solid-state active heat pump which transfers heat from one side of the device to the other side against the temperature gradient, with consumption of electrical energy. Hermetically sealed package include active element with monolithic immersion lens and thermistor assembled on a cold finger of TE cooler. The detector enclosure is filled with a mixture of heavy inert gases – krypton and xenon. Package also holds a chemical absorber of residual active gases (water vapour, CO2, oxygen and others), ensuring fault-free device operation for many years. Detector is also equipped with 10 mm diameter ZnSe window: rugged and less vulnerable to rapid temperature changes. The drawback of this material is its 70% transmission due to reflection losses. Two-sided antireflection coating has been suggested for transmission improvement, increasing the parameter above 90% in wide spectral range.
Photoconductor:
Several options of photoconductive detectors for Emphasis air monitoring subsystem have been considered:
- detectors with hyperhemispherical lens with 2.5 mm diameter (PCQI) and different detector temperatures (2TE, 3TE, 4TE)
- non-immersed detector (PCQ)
A comparison of particular detection modules and their parameters were made in the work (Figure 6).
Taking into account that returned signal power is very small, non-immersed detector is useless. An efficient way to achieve an effective concentration of radiation is to immerse the photodetector to a hyperhemispherical lens.
The practical (photoconductor) device was based on MOCVD grown structures. The main work was focused on optimization absorber thickness in order to suppress possible interferences inside the detector. New design should ensure almost full absorption of radiation in a single pass of the absorbing layer. Structure for photoconductor was optimized with analytic simulations and later on grown in VIGO's epitaxial system (Figure 7).
An active element monolithically integrated with hyperhemispherical microlens was mounted directly at the top of TE cooler (Figure 8). In order to achieve minimum temperature of active element sapphire chip carrier was removed. Cooling to 210K was necessary to get required detector performance. This implicates the use of 3- stage Peltier cooler. One of the biggest challenges (from the mounting point of view) was centring the microlens and making of wire connection between metallization pads and TO8 pins.
The quadrant detector is followed by four channel preamplifier, where each channel consists of two amplifying stages. First of them is a transimpedance amplifier, with ability to control the detector biasing voltage and compensate the bias current (to avoid amplifier saturation). The second stage is a noninverting voltage amplifier, with variable gain and output voltage offset compensation. The mentioned above parameters are set independently for each channel. Designing the preamplifier, it was mainly focused on achieving low noise level, low input impedance, stability, in band gain flatness, and reaching sufficient cutoff frequency (around 160 MHz). Due to the small enclosure size, and therefore limited heat dissipation ability, the current consumption must have been reduced, and it is also the reason of very strict supply voltage. The IR module case is designed to cooperate with external radiator attached to the front side of the module, however, if necessary, it is possible to use especially suited radiator and the cooling fan mounted on the enclosure top side (Figure 9). Detection module prototype was sent to Cascade in order to integrate it with air monitoring subsystem.
Photodiode:
The device is a Peltier cooled reverse biased immersed photodiode, based on MOCVD grown HgCdTe heterostructure. It features wide optical (3-11 µm) and electrical (~1 GHz) band along with high sensitivity (D*~1010 cmHz1/2/W for >8 µm wavelength).
The device reflects detector concept developed over the last two decades at Vigo (Figure 10). The device is equipped with an immersion (hyperhemisphere) microlense – infrared (IR) concentrator, monolithically integrated with detection structure, and IR retroreflector so as to further enhance IR absorption and shield against background radiation. The heterostructure is a modified PIN photodiode that consists of a narrow bandgap p-type absorber and wide gap heavily doped contacts: N+ - the contact for electrons and P+ - the contact for holes. The absorber is interfaced to the contacts with graded gap regions. The bandgap of N+ and P+ layers is taken sufficiently large to make thermal generation low and prevent injection of electrons (minority carriers) to the absorber. The composition and doping of the interfaces of the absorber are selected so as to eliminate parasitic barriers for electrons and holes that could impede collection of the photogenerated carriers. The p-type HgCdTe alloy is a material of choice for the fast response which is achieved by fast transport of optically generated charge carriers from absorber to contacts. Low gap heavily doped n+ layer allows for small (10 5 Ω×cm2) contact resistances for all contact metals used (Au, Ti, Cr, In).
Fabrication of the photodiode involves optical and electrical epiwafer characterization, photolithography, etching of mesa structures, passivation of mesa sidewalls, contact metallization, dicing of wafers into chips with single-element devices, preparation of immersion lenses, indium bump bonding to sapphire carriers with metal lead-outs, mounting of the chips on cold finger of Peltier coolers, sealing of detector elements in TO-8 packages filled with xenon or xenon/krypton mixtures (Figure 11).
The detectors are characterized by measurements of current-voltage curves, spectral responsivity, frequency dependent noise and time response. The time response measurements are performed with detectors coupled to microwave 50 Ohm or transimpedance preamplifiers constructed at Vigo System SA. The preamplifiers also provide tunable bias voltage in 0 2 V range. Amplified signals are registered with fast oscilloscope of nominal 8 GHz bandwidth, 40 GS/s single shot sample rate and <9 ps rise time.
Two types of pulsed IR radiation sources are used in the time response measurements (Figure 12):
- quantum cascade lasers (QCL) producing 4-100 ns pulses of monochromatic radiation
- optical parametric oscillator (OPO) as a source of short ~25 ps pulses of radiation, tunable in a wide spectral range from UV to 16 µm
The time response measurements are done under conditions allowing for revealing slow components of time response, i.e. at excitation by long 50 100 ns radiation pulse from QCL or short pulse of sufficiently high intensity from OPO. The time constant of the slower component at the tail of signal pulse is used as a parameter characterizing speed of response for various operating conditions.
Photodiode was integrated with one channel preamplifier. Mechanical design of detection module was adopted to Cascade air monitoring system (Figure 13). The preamplifier implements classic idea of transimpedance preamplifier basing on two RF transistors. First transistor acts as voltage preamplifier in common emitter configuration. The following stage is a buffer and impedance converter in common collector configuration. The whole available preamplifier high cut of frequency is ~ 1.4 GHz. In current design, the top frequency is limited to improve the stability and reduce wideband noise. Negative feedback was introduced, therefore the preamplifier is stable within whole bandwidth, and the frequency response is smooth.
Additional activities within EMPHASIS project; “SMART” IR detection module:
Vigo System S.A. has also developed “SMART” IR detection module, which is especially suitable for testing and development purposes. New module cooperates with intelligent TEC controller and allows the user to configure the following parameters with the PC software or user interface (Figure 14):
- detector bias voltage
- compensation of the bias current
- preamplifier first stage transimpedance
- compensation of the frequency response of the first preamplifier stage
- coupling between first and second preamp stage: AC or DC
- compensation of the output DC offset
- preamp bandwidth
- second stage voltage gain
The SMART IR module also offers the ability of monitoring important voltages in the circuit:
- detector bias voltage
- voltage after the first stage and voltage at the preamplifier output
- supply voltages
- TEC & thermistor lines voltages
Optimisation of wirebonding for VIGO detectors:
Wirebonding is a method used to attach a fine wire, in this case 25 m in diameter, from one connection pad (metallized bond sites on interconnection substrates) to TO8 pin, completing the electrical connection between detector and TO8 pins.
The main stages of wirebonding for VIGO detectors are:
1. Making of electrical connection with a gold wire Ø25 µm between active element of detector and each stage of thermocooler (with using two-component epoxy resin Epotek E415G)
2. Making of electrical connection between the first stage of thermocooler with pins of TO-8 sub-mount with using Epotek E415G
All mentioned above steps are handmade which are time consuming and operator depended. Wirebonding optimisation was an attempt to establish bonding parameters in semi-automatic wirebonder (Figure 15).
This work showed that there is a possibility to make a semi-automatic wire bonding connections for VIGO detectors using Aluminium wire (Figure 16). One of advantages of using aluminium wire is its bondability to TE ceramics substrate.
Wire bonding with gold wire was also evaluated. Unfortunately, gold wire does not stick to ceramics and that is why there is a need to design and manufacture metallization pads on TE ceramics substrates. What is more, bonding surface must be heated which may be dangerous for detector. Semi-automatic wire bonding with gold wire requires more R&D work at the moment.
Summary:
VIGO System S.A. developed and manufactured five IR detection modules for Emphasis air monitoring subsystem. First detection module was based on quadrant photoconductive detector and four others were based on photovoltaic detectors.
Newly developed photodetectors and detection modules extended VIGO System products line (QIP series). QIP is the four channel, transimpedance, AC or DC coupled preamplifier and it is dedicated for BenchTop or OEM laser beam positioning applications.
WP 6
Within the EMPHASIS project work package 6 the goal was to develop and test two imaging stand-off trace detection systems. A Raman-based system tested by FOI and an infrared backscattering based system developed by Fraunhofer IAF.
Active Imaging IR Laser Backscattering Spectroscopy:
The IAF imaging IR standoff detection system is based on laser backscattering spectroscopy. A widely tunable quantum cascade laser is used to illuminate the scene and the backscattered light is detected by a high performance infrared imager. By step-tuning the illumination wavelength and synchronous image acquisition, a hyperspectral image is obtained, where each image layer is associated to a specific illumination wavelength. Thus, each pixel vector corresponds to a backscattering spectrum at a specific location in the scene.
An especially interesting region of the infrared part of the electromagnetic spectrum for the goal of chemical substance identification is the molecular fingerprint region between 7 µm and 10 µm, as most organic substances show characteristic spectra in this range (Figure 17). A further advantage is the transparency of the atmosphere, which is a crucial condition for targeted measurement distance, as well as the high power thresholds established by the legislature for eye-safe laser operation.
The spectral measurement range of the detection system is dominated partly by the spectral cut-off and sensitivity of the IR imager in use, and – maybe even more important – by the tuning range and illumination power of the IR laser in the setup. There are only few laser sources that match the challenging boundary conditions required by the spectroscopy system in this spectral range. In the last few years, Quantum Cascade Lasers have emerged as reliable laser chips that are able to cover the required broad tuning range with high spectral brightness and output power and thus constitute the source of choice for application in the backscattering spectroscopy system. Within the EMPHASIS project a new Hetero-Cascading quantum cascade laser structure has been designed and according active chip material has been produced with a tuning range specifically tailored to optimize detection performance for the target substances defined in the EMPHASIS substance list. During epitaxial growth of the wafer material, two gain regions centered at different wavelength are combined. With this approach in one chip the tuning range can be enhanced by about 50 %. The QCL chips are operated in an external cavity setup in Littrow configuration. The collimated beam of the chips front facet is reflected by an optical grating, which is used as wavelength selective element and mounted on a rotation stage (Figure 18).
One of the key goals for the IR backscattering spectroscopy system in the EMPHASIS project was to extend the measurement distance. This was achieved by mounting a wavelength-customized Ritchey-Chrétien-Cassegrain telescope for collecting the backscattered infrared in a front-looking geometry (Figure 19). The entrance aperture of the new collection optics was enlarged to 12.5” diameter in order to reduce the f-number. This enables high spatial-resolution hyperspectral imaging in the desired distance range. A visible camera was aligned with the infrared imaging optics that yields a calibrated visual image of the scene. This extension both simplifies system operation, and moreover supports the operator by identifying contaminated objects in the scene, that produced positive alarms in the hyperspectral image.
An additional goal within the EMPHASIS project was to broaden the scope of detectable target materials. This included adding pre-cursors of actual explosives like Ammonium Nitrate (AN). IR backscattering spectra of some common explosives like PETN, RDX and TNT was compared to the backscattering spectrum of AN. It was quite obvious, that in the formerly measurable wavenumber range over 1100 cm-1 AN has a fairly even spectrum, that shows far less characteristic features then PETN for instance. It was therefore necessary to extend the system’s spectral measurement range by adding an additional laser illumination module, that covers the spectral range from 1000 cm-1 to 1180 cm-1 (Figure 20).
A crucial part of the imaging IR backscattering detection system lies within evaluation of the resulting spectroscopic measurement data. Though the target material spectra are known as they can be measured in advance and thus a spectral target library is not difficult to establish by measuring the pure target substance on a non-scattering surface, the target material might be spread on a strongly scattering surface in a real-world measurement. In this case, the measured target spectrum is (linearly) mixed with the surface-spectrum. As the substance spectra is not known in a general measurement scenario, un-mixing becomes a non-trivial task and thus effort was put into development of customized target detection algorithms.
Stand-off Imaging Raman Spectroscopy:
During the 1st period of the EMPHASIS project a 532 nm imaging Raman system was tested and validated to be a very promising technique for particulate trace detection of explosives/precursors. However because of the risks to skin and eye associated with the 532 nm laser used, focus was instead shifted to testing the 355 nm eye-safe corresponding system that was built up.
Work performed while building the 355nm system has included: optimisation of imaging algorithms, improvement of GUI, and redesign of optical construction. In the system communication protocol parameters for image acquisition specification have also been set between Fraunhofer IAF and FOI.
FOI has together with a Finnish research company, VTT, developed a UV filter prototype necessary to build a 355 nm imaging Raman system which now allows for detection in the UV range (Figure 21).
In Emphasis, the initial tests of the imaging UV-Raman demonstrator system was performed by measuring sub milligram amounts of ammonium nitrate placed in holes in an aluminum plate. The diameters of the holes measured 1 mm and 0.3 mm respectively (Figure 22). The amount of ammonium nitrate in the larger holes, based on hole-geometry and ammonium nitrate density, is estimated to be about 500 µg while the smaller ones contained below 50 µg. The extracted spectra from the hyper spectral image cube created during the measurement show that it is possible to detect the ammonium nitrate in the smaller holes which is estimated to be about <50 µg (Figure 23).
The prototype filter capability was thoroughly evaluated at FOI during the fall of 2013 and discussions on how to make the filter even more efficient has been performed. VTT has delivered a first filter product and tried to optimize the filter since the first delivery during 2014. In total, three filter prototypes have been manufactured and a fourth was stopped since it did not appear to provide any improvements. There are in total two major versions of technology that has been evaluated.
The work on optimization has not resulted in any more detection sensitive filter product than what was used during the final part of the project. The filter and the imaging UV-Raman system has been tested significantly in the EMPHASIS project and the system used at the final demonstration is the best version that has been achieved and has the capability in the range of the above described.
During the final project demonstration in September 2014 the system was placed inside a building aiming at a car door on ~10 m distance. On and around the door handle different precursor particles were applied and the system detected and identified them. The result was presented by showing where on the target surface the different substances are detected, also the threat level (certainty) was displayed. It has now been shown that the imaging Raman technique also can work in an eye-safe way without sacrificing much of the performance.
Orthogonal Image Analysis:
The UV-Raman and mid-IR-based detection techniques proved to be complementary regarding their sensitivity to different compounds. While both techniques rely on a spectroscopic approach and are therefore in principle able to identify a wide range of different materials, there exist large differences in signal strength as well as in the significance of spectral information gathered from the scattered light for the various compounds of interest. The studied techniques in the EMPHASIS project are both very useful for confirming if explosive traces are deposited on suspicious objects. This type of intelligence is of valuable use for police forces and the different detection principles of the techniques provides a basis for covering a broader range of target compounds that can be detected. In addition, when the capability is overlapping the detection results can be co-supported and thus the confidence of the results will be enhanced. For the IR system, it was found that most compounds provided measurable signals. However, there are strong differences in the significance of the backscattering spectra. For example DNT (precursor to TNT) provides a highly characteristic spectral response, easily distinguishable from TNT, which is more difficult using standoff imaging based on UV Raman. Other examples of substances with “good” IR spectra are HMT or PETN. On the other hand, the spectra of e.g. KNO3 and even more KClO3 show less distinct spectral features, while Ammonium Nitrate ranges somewhere in between. Substances like KClO3 are still identifiable by IR spectroscopy, but the much lower spectral significance will render detection difficult especially on interfering substrate materials. UV Raman that uses a 355 nm laser, on the other hand, gives a very high significance of spectral information for almost all substances but have several orders of magnitudes lower signal strength compared to IR backscattering. The limit here is thus in the effective Raman cross-section for the substances that sets the detection limit. Nitrates and chlorates that are less favorably detected by the IR technique, are the compounds that show best performance for UV Raman, while it encounters difficulties to detect DNT, TNT and some other substances due to the lack of signal intensity. Especially for small trace particles. In the case a 532 nm laser is used, the sensitivity is enhanced to a great extent for compounds such as TNT, PETN, RDX, TATP, ammonium nitrate and chlorates etc. As the two techniques operate at non-overlapping regions of the electromagnetic spectrum, the measurement data is independent as in consequence is the probability of false alarms for each measurement method, alone. Separate data analysis algorithms are applied to the hyperspectral images produced by the two imaging sensors, providing a 2D detection map each. Fusion is then accomplished on the bases of the detection images. This approach also allows introduction of weighting factors on the individual decision outputs to improve the cumulative system sensitivity. This is the fusion level of choice, as the false alarm probabilities of the two system specific data analysis algorithms multiply and hence the cumulative probability of false alarms is vastly reduced. Taking into account the above consideration on substance detectivity, it is inviting to introduce substance specific weighting. This means e.g. that the detection outcome of the IR imaging system can be given greater weight than that of the Raman system for substances that have well distinguishable IR spectra but poor Raman spectra, and vice versa. In addition, this approach allows the hyperspectral image analysis algorithms for each sensor to be optimized to individual requirements that may vary slightly. In the EMPHASIS framework, both the imaging Raman and IR spectroscopy systems communicate detection results via the EMPHASIS network to the central command center, where the data is collected and presented to operations staff. By overlaying the measurement results of the two sensors, the decision fusion implementation is provided inherently.
Optical System Configuration:
Detection performance was increased by measures for beam shaping and despeckling. Instead of using a Gaussian shaped collimated beam, providing high intensity in the center at the cost of a rapidly decreasing S/N ratio towards the outer regions, one would like to work with a homogeneous intensity in the illuminated area, i.e. a top-hat beam. Another deteriorating effect is so-called laser speckles, stemming from the coherent nature of the illuminating light. Interference from scattered light at “rough” surfaces (on the scale of the lasers wavelength) disturbs the image quality. Although appearing like additional noise, this effect is deterministic and will not average out simply by longer measurement times. Instead, many different speckle patterns have to be created by varying the illumination conditions. We addressed both issues by coupling the laser into a home-made narrow rectangular waveguide via a fast scanning, resonantly driven 2D-MEMS mirror, providing both homogenization as well as the necessary angle diversity for the creation of statistically independent speckle patterns. The MEMS scanning periods had to be synchronized with the camera frame rate and projection optics were adapted to the size of the waveguide and the FOV of the telescope optics. The developed method is both fast and provides sufficient optical throughput.
Detector Adaption:
Evaluation of a more cost-effective IR standoff system using micro-bolometric imagers revealed that the currently achievable signal to noise ratio does not provide sufficient data quality for reasonable detection results at this time. However, development progress on both detector and illumination side still renders this option interesting for future cost optimization.
During the EMPHASIS project demonstration, both imaging stand-off detection systems successfully found trace amounts of various explosive precursors placed on different objects, e.g. parts of a parked car at a measurement distance of approximately 15m (Figure 24). Test substances included DNT, HMT, Fertilizer and many others (Figure 25). A full spectroscopic measurement together with the required data processing and analysis amounts to slightly less than 20s for the IR backscattering system. The standoff detection systems proved to be fully operational under near-real world conditions (Figure 26).
WP7
Emphasis Network System:
The main objective for WP7 was to specify and implement the system communication infrastructure to provide the Emphasis system with the necessary functionality for wireless and secure data communication between the different sensors (WP4, WP5 and WP6) and the central system responsible for information management, data fusion and presentation (WP8).
At an early stage of the project a concept study was carried out resulting in an internal report: “Emphasis System Network Concept Study” discussing different radio technologies applicable for the different Emphasis sensors. A specific concern was the sewer sensors considering their locations where wireless radio communication was assumed to be difficult.
During the study some real-life tests were performed including public mobile network devices as well as 27MHz and 455Mhz handheld FM transceivers (Figure 27).
The study concluded that both the transceiver solution and the public GSM network would be sufficient for the Emphasis requirements. In order to simplify the development the study also proposed to only use the GSM network in the project (Figure 28).
Followed by the concept study a system architecture definition was produced resulting in a system design specification.
Partly based on the developments within the predecessor Seventh Framework Programme project LOTUS the design specification defined and specified:
- Common hardware (“Router”) and software used to interface each sensor with a wireless network
- Communication protocols for secure data transfer beween sensors and the central system
In order to be able to utilize as much as possible of existing infrastructure and standards the Emphasis Network System (Figure 29) is based on communication via the public mobile network and as far as possible, uses standards like XML (Extensible Markup Language), NMEA (a GPS data format defined by National Marine Electronics Association) and OpenSSL (open-source implementation of SSL/TLS encryption functionalities).
The Router device developed within WP7 includes:
- An XML-based protocol, common for all different Emphasis sensors (as well as sensors developed within the LOTUS project): the implementation have only two requirements on each sensor:
o A physical Ethernet interface (RJ45/twisted pair)
o A HTTP server delivering XML-formatted data
- Wireless communication facilities in terms of a GSM radio module
- A GPS receiver for real-time positioning
- Environmental sensors for real-time collection of temperature and air humidity
- Storage space for collection of data in a case of interrupted wireless communication
- Software for data transfer between sensor-router and router-central system
- Software for encryption/decryption of data
- A web-based configuration interface
A total of ten new Emphasis Routers (Figure 30) were assembled and in addition three Routers inherited from the LOTUS project were updated both hardware- and software-wise to comply with Emphasis requirements.
The first version of the Network System was tested during an on-site field-trial session at FOI in Sweden in October of 2013. The field-trial involved the Cascade IR-sensor, Fraunhofer-ICT sewer sensors and Routers with measurement sources in the form of vapours from HME-manufacturing and sewer water contaminated with residuals from HME-manufacturing. Live sensor data was also transferred to the central system developed and managed by TNO.
The tests resulted in software updates and also revealed the need for data communication simulation software. The simulation software developed from late 2013 to early 2014 not only simplified the Router communication software development but also the sensor integration efforts.
During the first part of 2014 the partners developing sensors (Cascade, Fraunhofer-IAF, Fraunhofer-ICT and FOI) were supplied with Router hardware for final integration with the different sensors. In this period the complete network system was also verified, documented in a System test and verification report.
At the final Emphasis demonstration in late September of 2014 eleven different sensors/routers were deployed simultaneously and sending live data to the central system presented at the test site in real-time.
A summary of the results from WP7:
- It is possible to build a highly scalable, wireless, low-power, sensor network at a low cost using existing components and infrastructure
- The idea of connecting sensors in a scalable network adds a lot of value in terms of real-time response, sensor surveillance etc at a low cost (significantly lower than sensor costs)
- It is convenient for sensor manufacturers to have a standardized software/hardware interface not having to deal with data format specifications, security, communication etc.
- If a sensor network shall be used in non-urban environments with poor or none-existing wireless infrastructures other means for data transfer (e.g. proprietary radio communication or physical, periodic data collection) must be considered
WP8
Agent based approach: The computer software structure is based on agents. In computer science, an agent is a part of the software that acts on behalf of a user or other program. The idea is that the agents activate themselves when needed and each and every task will require its specific agent. For example, a specific agent is used to calculate the probability of the presence of a bomb factory based on a measured concentration. Another one is used to combine the probabilities obtained from all sensor readings into one probable location area. The use of agents allows for a very flexible processing. Specific tasks can be added by just adding applicable agents. The agent structure allows seamless up scaling and introduction of new sensors. In EMPHASIS this flexibility has proven its added value: agents were added that allowed data from BONAS sensors to be included in the EMPHASIS processing. Additional agents made EMPHASIS sensor data available for BONAS.
Data fusion and information management: Technology development has been focused towards:
• reliable detection of bomb factory while achieving a low false alarm rate
• exact location of the bomb factory based on measurement with multiple sensors, while taking into account dispersion of gases in air (including influence of wind direction and speed)
In the EMPHASIS system many sensors used on roofs of buildings and in sewers provide a large amount of data that is fused and analysed in an innovative way. Sensor input is processed in a three stage approach (Figure 31).
The first stage is the object assessment. Based on sensor readings, clouds (either a gas cloud in the air or a solvent cloud in sewer water) are determined. Specific is the processing of scarce sensor data, measurements are not available for any point in space, for any point in time. The second stage is the situation assessment: the determination of the location of the bomb factory. The situation assessment will not directly provide one single location. Instead, it will create a source probability map, giving the probability that a bomb factory is at a given location. The third stage is asset management; the placement of sensors, their routing, the control of their scanning, their targeting, all in order to improve the effectiveness of object assessment and situation assessment, until ultimately the location of the bomb factory is fixed.
Actual implementation is using a layered approach (Figure 32). The layers are:
• Measurement
The processed sensor readings for the concentration of a given substance.
• Map
To relate all physical locations to an easy human understandable format.
• Dispersion
To calculate the likelihood of the source location, based on dispersion of the substance in air (dilution in sewer).
• Prediction
Determine the likelihood of the source location based on measurements of multiple sensors.
Each of the layers has its own agents.
Results: The current Emphasis implementation has brought sensor network based explosive detection beyond current state of the art:
• Processing of chemical sensor data, taking into account the multidimensional (2D and 3D position, 1D movement (sewage) or 3D expansion (gas cloud)).
• Application of agent based processing using artificial intelligence technology.
• Use of a sensor network while being largely independent of actual sensor locations (no need for a grid or a predefined pattern for sensor lay-out).
WP9
The feasibility study encompasses the evaluation of the possibility for applying the technical solutions from the other work packages at realistic urban conditions. The question of whether the proposed technical solution can be transformed in a business form and how the system alerts will impact the system cost has been studied.
Modeling bases have been defined to determine the context of the project. These issues were addressed separately in the sewers and in the air. Feasibility of the EMPHASIS system is really close to the environment tested. Both for sewer system and in the air, the density of population and the urban class are determinant parameters which can modify a lot the behaviour of the air system. The delivery summaries all the settings that should be taken into account to model the behaviour of the system in a specific area.
The cost effectiveness study is a benefit-cost analysis (BCA) and a decision-support tool. The methodology used for this study is based on the methodology used for industrial safety projects. The management of industrial risks raised numerous questions, which require more than ‘yes’ or ‘no’ answers:
- Which criteria should society use to decide that the level of risk of an industrial facility has been reduced as low as reasonably practicable?
- How should society arbitrate between very different criteria such as possible death and injury caused by an industrial accident, environmental impacts of industrial activity and the cost of safety mechanisms, which impact numerous stakeholders?
First, we tried to quantify directs costs (installation, maintenance and running costs of the system) and indirect costs (opportunity costs, like the loss of freedom) and also direct benefits (about the willingness to pay of the avoided damages, and the enhancement of the safety for the society …) and indirect benefits (reduction of surrounding risks).
The study of legal aspects showed that the different components of the sensors network of EMPHASIS are not subjected to the same legal issues. The sensors installed in the sewage area would probably not be challenged under the provisions of the European Convention on Human Rights. The area monitoring subsystem, which generates electromagnetic waves at a large scale, may jeopardize the right to a healthy environment as it is protected in the wake of Article 8 of the Convention. As for the mobile units subsystem, which could aim private housings' entrances or windows for instance, or even persons in the street, it could certainly be challenged under the provisions of Article 8 as causing potential interferences to privacy and to its foundation, the physical integrity and individual well-being.
However, such interferences with human rights are not inevitably unlawful, since they can be justified by proper legal provisions in accordance with the rule of law. Therefore, the operation of EMPHASIS shall be supported by a specific legal framework, for instance at national level, which would establish the conditions of an effective control of the surveillance measures and the possible judicial remedies. Finally, in some specific circumstances, the States would be entitled to set up the system for a limited period of time, even though it would breach the Convention, for instance in case of a permanent and actual risk of terrorism, materialized by bomb attacks.
Societal acceptance issues studied are the public acceptance of technologies contributing to enhance security for society and citizens but creating potential risks to public health and the operational acceptance by the various stakeholders of Improvised Explosive Device (IED) manufacturing localization.
A data collection process has been achieved in order to achieve those objectives. Studies of expert reports, European project and press on the one hand and on the other hand realization of a focus group on the other hand have been conducted.
For this study, stakeholders coming from various entities have been interviewed. During these last 6 months, an interview has been conducted with the National Coordinator Counter-Terrorism and security (NCTV) of the Ministry of Security and Justice of Netherland and a focus group has been organized with French actors. Representatives were:
- the General Secretariat of Defence and National Security (SGDSN) in the technological and prospective pole,
- Legal adviser for the General Director of the National Police (DGPN),
- Explosive section of the central laboratory of Police (LCPP) – chemical risks pole
- And the French EMPHASIS partner, INPS.
Following questions were asked to these professionals of IED prevention to launch discussions:
• Can EMPHASIS system create a social problem on privacy, confidentiality, or safety? People talked mainly about the intrusion of privacy, the public health issue, the cost for public finances and the nuisance of the technology or of the use of the operators.
• Can users reject EMPHASIS system, due to the utility, the usability or the acceptability? Discussions talked about the cost and budget rate and the staff, the necessary changes for an efficient organization to support this system, the user’s acceptability and the interoperability with other systems.
• Could the human and organisational factors variability make resilience to EMPHASIS system? Main discussions were around the evolution of the perception for actors of society and the communication strategy, the evolution of the law, the cost of organization and cost of the system maintainability, the complexity of the chain of actors (decision time), the necessity to manage data collected and the implementation of safeguards in case of false alarm and a strict policy of compensation in case of false arrest.
Then we studied the deployment options. First, significant criteria which could impact the deployment options are extracted from each previous study. Then, risks and consequences assessment methodology on projects were studied. Then, we defined three deployment scenarios for the EMPHASIS project for which we choose concrete examples:
- A system temporarily deployed on a sensible site. Example studied is the G20 summit, November 3-4 2011, Cannes, France,
- A system for a whole district monitoring in high vigilance. Example studied is La Défense business district, Paris, France.
- A system occasionally deployed for a targeted area monitoring for emergency surveys.
These examples are used to estimate the coarse costs distribution, equipment, setup and operating costs, maintenance benefit, frequency of use and lifecycle for each case. Finally, a comparative synthesis balances each cases of scenario.
Public acceptance of an innovative technology is a major issue for innovation, for security technology is even more important due to specific constraints such as the trade-off between explaining technology purpose and characteristics and making this technology effective to prevent unwanted IED-based events.
We consider different approaches. A state of art of studies and projects related to societal acceptability of innovative technology allows the identification of a set of studies the results of which can support the study of the EMPHASIS acceptance issue. Focus Group and questionnaires and an interview dedicated to EMPHASIS acceptability have been organized in order to discuss this issue with stakeholders. Finally reactions to press publications about EMPHASIS have been studied.
This study converges with results that EMPHASIS acceptance issue is complex and is a trade-off between ethical values on the one hand and the necessity of some secrecy on the other hand. This trade-off depends among other dimensions on public perception of IED–based risks, of their trust in their government, and their priorities on the use of public money. Those dimensions are variable from one country to another and may vary in time and with the occurrence of IED-based events. Definition of this trade-off will be a basis of the definition of communication strategy on EMPHASIS system and the associated development of an IED culture.
The D9.2 report estimates directs costs (installation, maintenance and running costs of the system), indirect costs (opportunity costs, like the loss of freedom) and also direct benefits (about the willingness to pay of the avoided damages, the enhancement of the safety for the society …) and indirect benefits (reduction of surrounding risks).
To conclude, the final decision for the EMPHASIS project stays a political decision and is primarily an opportunity decision that cannot be taken without a precise assessment of the current situation and, of the balance sheet of benefit-costs of each option.
WP10
The objective with this work package was to test and validate the subsystems of the EMPHASIS concept. The work ended with a demonstration of networked subsystems.
At the second project meeting in Paris, the coordinator and partners started the discussions on what should be included in the end of the project concerning the validation and demonstration of the EMPHASIS system. This resulted in a general overview on how to address this topic concerning some scenarios for improvised home-made explosive manufacturing. Moreover, it resulted in a good information to the partners on several practical issues e.g. availability to the sewage system, handling and regulations of explosive work at FOI etc. During the following project work and meeting the report on the Test plan was completed by FOI and distributed to the consortium. It was decided at the fourth project meeting that the final validation will be performed in September, 2014. The test plan for the final validation event was updated around the time of the fifth project meeting since it was decided to do a joint final validation with the EU FP7 project BONAS. This project is a parallel project to the same FP 7 call as EMPHASIS works on.
In EMPHASIS, almost all of the subsystems were validated at the end of 2013 and full completion was expected in June 2014.
The final experimental validation event has been performed in collaboration with the BONAS project. The final event was conducted on September 24-25 at the FOI test site Grindsjön 40 km south of Stockholm. The event was a two day activity with experimental contents the both of the days with emphasis on the first day.
The updated test plan was the base for the detailed practical work that was carried out between the sixth project meeting and the validation work carried out in September. The number of sensors provided from both the EMPHASIS and BONAS projects and their respective capacity needed to be taken into consideration for realising the aims of all the experimental activities.
The coordinator for EMPHASIS visited the BONAS project demonstration in Rome, Italy, in the beginning of June 2014 to further build up the knowledge about the project contents and sensors in BONAS. This was a very beneficial meeting in order to create a strong collaboration between projects and also to describe the practical possibilities and limitations that at this time could be anticipated for the joint final event. The type of compounds and scenarios was discussed on and also the timing of arrival of partners to the FOI test site in order to be prepared for the validation day. This meeting also included discussions on how to use the projects respective sensor data and how the data could be fused. The following work sorting on how to use sensor data across the project was intensified from June to September, 2014.
Subsystem testing and validation has been performed for the system communication network, the sewage monitoring and area monitoring subsystems. The experimental testings occurred at the FOI test site 40 km south of Stockholm during October 2013. Precursors to explosives in vapour phase and in the sewage were measured in realistic scenarios. The work with the area monitoring subsystems provided in-depth knowledge on how to configure/deploy sensors according to the proposed scenarios. The experimental work gave knowledge from the results that pointed to the capacity this type of system has. The sewage sensor subsystem was configured and installed in the local sewage pipes at the FOI test site. Relevant compounds were detected in the chosen scenarios and knowledge on how to make a better set-up for the validation event was acquired.
The stand-off imaging IR and Raman detection devices for traces of explosives/precursors was jointly validated in early June 2014. Personnel from Fraunhofer IAF with sensor equipment arrived at the FOI test site for joint experimental work. This work also continued the days before the final validation event in order to secure the functioning of the subsystems. Hitherto they have been extensively tested at each of the organisations labs, however, standalone from each other. Data communication of sensor data was evaluated as well in order to make sure that the EMPHASIS central system was able to receive the data. For this purpose the work on stand-off detection (WP 6) relating to the software interfaces between sensors, communication system (WP 7) and central system (WP 8) were the basis from a technical perspective.
The final validation event for the project was performed on September 24-25, 2014 (Figures 33-41). The numbers of participants were 94 with in total 13 countries including USA.
Both of the projects, BONAS and EMPHASIS, collaborated in the experimental demonstration. In addition, the previous project LOTUS was also included in the activities in terms of the inclusion of three of totally four mobile sensors. The LOTUS project concerns the mobile sensors for precursor detection mounted in roof-top boxes of vehicles.
All detection results during the demonstration were transferred to the central system and displayed. The data stored can be replayed afterwards the continuous detection and display of data. The communication with BONAS and LOTUS devices proved to be operational.
The details of the experimental demonstration are reported in classified reports of the EMPHASIS project.
Potential Impact:
Hindsight always makes solutions to problems so much clearer than at the time of their occurrence. For example, today we are aware of many risks including the high jacking of planes and their purposeful crashing into civilian buildings, with devastating effects to public well-being. But in the morning of September 11, 2001, no one would foresee that such an event was just about to happen. This was simply a failure of our imagination.
Even if we could create the perfect bomb-mitigation system, the terrorists might eventually find a way around that system. This is the foundation for dealing with the problem in multiple fronts, i.e. considering the entire terrorist timeline, from the bomb material supply chain to the detection of bomb factories and from the handling of an identified bomb-threat to the reconstruction of a crime scene. The earliest phase of them all relates to the possibility for discovering terrorists and stopping bomb attacks. This, in turn, relates to the issue: who is a terrorist and what can be done to prevent people from becoming terrorists? Today, there is no clear and widely accepted definition on terrorism, other than it apparently involves the use of violence or the threat of violence for the purpose of obtaining control, power and obtaining political goals: effective ways of releasing fear and causing destructive consequences for society and citizens globally. A significant amount of research effort has been expended on the issue of why people choose to become terrorists. Nonetheless, convincing groups and people to feel and develop destructive thoughts and terrorist actions should have a significant priority and should be a long-term preventive method.
The first known large-scale use of IEDs was during World War II and ever since IEDs have been used both for unconventional warfare in military theatres of operation such as in Iraq and Afghanistan and in terrorist attacks such as Bali (2002), Madrid (2004), London bombings (2005) and more recently in Oslo (2011) and Boston (2013). The threat of terrorist attacks is consequently a very real concern for citizens in many parts of Europe and elsewhere in the world. IEDs can be manufactured from military and commercially based explosives or home-made explosives and often a combination of these are used in terrorist attacks. Fundamentally, terrorists use whatever is easily available for the preparation of bombs and due to the wide range of options in this respect there are numerous parts that comprise the threat to the society.
The Bali bombs, 2002, were manufactured in a two-story house a few kilometres away from the terrorist attacks resulting in hundreds of dead and injured people. The bomb factory had not been disturbed since the bomb makers departed and forensic experts could make a vast amount of analyses. The bombs were found to be based on a combination of potassium chlorate and aluminium powder.
Both of the substances used in the Bali bombs are non-volatile and unrealistic to find in air, however, it is likely that these can be detected as traces in the vicinity of bomb factories or in the waste water pipes originating from such facilities.
In March of 2004 in Madrid, ten bombs against the commuter train system exploded due to a coordinated terrorist attack resulting in hundreds of killed and injured people. Shortly after the attacks the police identified an apartment in Leganés in south of Madrid as the likely bomb factory. The suspected people trapped in the apartment set-off their explosives resulting in killing themselves, nevertheless, investigators later found out that the explosives used by the suspects were of the same type as those ten bombs used on 11 March. The bombs were found to be made of Dynamite probably bought from a retired miner who still had access to blasting equipment.
Also for this terror attack an apartment was used as an IED manufacturing facility in an area with a large number of inhabitants.
It is evident that there exists an urgent need for new tools in the extensive work of preventing future terrorist attacks and this is a large scientific challenge in the security domain today for the development of systems for preventing the manufacturing of home-made explosives (HMEs) and stopping bomb attacks at an early stage. For the law enforcement services there is a large need for tools that contributes to the early discovery of bomb attacks at specifically the planning stage.
The preparation of an IED involves different phases, where planning and financing the operation is the first phase. Thereafter precursors are obtained either illegally or purchased legally and transported to the location where the preparation of the IED is performed. The phase before execution of the operation takes place in a so-called bomb factory, for example a kitchen or a garage, where equipment and chemicals are manipulated in order to create the IED. The discovery of bomb factories is of primary importance in the prevention of terrorist activities, where investigations can be conducted with fewer time constraints and with greater accuracy than in later stages. The detection of precursors complies with the “Early warning system concerning explosives”, which is “Priority 1” of the “Prevention measures” in the Action Plan on Enhancing the Security of Explosives. Recently the European Commission has released a regulation on the precursors available on the market.
Due to the large variety of HMEs that can be prepared, currently there are no specific commercially available sensors to survey the presence of precursors or the transformation of such chemical compounds into IEDs inside a suspected environment. The search, monitoring and identification of suspicious substances are also complicated by their different physical properties that they possess (vapour, solid, liquid). Specific EU FP 7 Security Projects have addressed this task (LOTUS, BONAS and presently EMPHASIS), considering strategies to put in place, giving priority to some precursors to be detected and supporting the development of specific sensors. The use of different sensors is not a unique answer to the detection of the threat but is a part of the toolbox needed to identify the suspicious factory.
A timeline for the terrorist preparations include several steps. In the planning and financing phase, terrorist plots may mainly be revealed through conventional intelligence gathering methods, e.g. surveillance of known terrorist groups, informants, monitoring of money transfers or intercepting the group in a robbery. In many cases, necessary household chemicals or chemicals readily available in hobby stores can be obtained at low cost and little effort. Monitoring trade of restricted materials may be one possible way to reveal terrorist plots at this stage if large amounts of material are purchased or stolen.
The preparation and production phase can by necessity be quite long (weeks to months). Unless the bomb-makers are quite professional they will need to test and practice the procedures and in many cases the chemical manufacturing process in itself takes considerable time. An example of the production time frame is the London attacks. The terrorists obtained hydrogen peroxide, one of the main bomb ingredients. “They could buy it as liquid in an 18 per cent concentration. Between the end of April and July 5, 2005, they are alleged to have bought 443 litres in either one-litre or four-litre containers.” They then reduced it to higher concentration in their kitchen.
Detection in the production phase has several distinct advantages compared to detection in the transportation phase. There is more time available for detection, some detected substances may be present in larger quantities, if a threat is detected, there is time to take further actions. During the production of explosives and even drugs or CWA, elevated amounts of precursors can normally be present in the air. Evidence of this is found in the reports by residents in the neighborhood around the Leeds “bomb factory” where the explosives for the London bombs of July 2005 were made. The bomb makers bought hydrogen peroxide in 18% concentration and “three members of the gang are said to have spent long hours sweating over the electric cooker in the small kitchen, boiling huge panfuls of liquid hydrogen peroxide to reduce the chemical into a stronger concentration.”
Regarding the smell, local resident John Langlan said:
“I think it was that strong around this area that it affected and killed all the plants and they have just started growing back now - that is how long it has taken”.
Detection during transportation is much more disadvantageous than detection during production. First of all, the detection itself is more difficult and the time frame for intervention activities is also much less as compared to the production phase. Furthermore, even in case of successful detection in the transportation phase, the interruption of the attack is not without risk. If the person carrying the bomb is a suicide bomber, the bomb may be detonated with severe consequences for law enforcement personnel as well as innocent bystanders. Detection during the production phase gives more time for law enforcement to act without risk for themselves or others. When the plot has reached the last phase - the attack itself - it will be too late and severe damages and casualties will be a fact.
The outcome from a system such as EMPHASIS would be to narrow down the search area of the illicit production to a couple of blocks or even pin-point the bomb factory. The data produced from a system such as EMPHASIS should be seen as intelligence information that needs to be complemented with other intelligence before any intervention activities are initiated. Furthermore, the EMPHASIS system would make it more difficult for terrorist to prepare HMEs without being discovered. The main benefit for finding bomb-factories would be the capacity to stop a devastating bomb-attack at an early stage with minimum consequences for society and citizens.
The virtue of the technology for the EMPHASIS central System is the ability to create awareness of a complex 3D environment using a network of randomly dispersed heterogeneous sensors. The awareness is highly reliable, on one hand by the low false alarm rate, on the other hand by its low “missed hit” rate. Due to the heterogeneous sensor set, it is virtually impossible to hide for the sensor suite.
Hereby the technology adds to the impact of the EMPHASIS system. In addition, a predecessor of the technology proved its value during the successful demonstration of the (EDA) ICAR project. Both projects have in common they act upon terrorist-like activities, work in a complex 3D environment and are searching for activities that the terrorists like to keep hidden.
Potential impact of the technology can be in the area of:
• Counteracting terrorism
o Countering bomb production (EMPHASIS)
o Denying the use of the RF environment (ICAR)
o Detection and tracking of Piracy activities
o Etc…
• Awareness in complex environments:
o Search and rescue
o Sea and land border patrol
- Countering illegal immigration
- Countering drug smuggling
- Etc…
o Surveillance
- Set a watch on complex extended objects like airports
- Etc…
o Monitoring of large infrastructures
- Pipelines
- Production plants
- Etc…
o Countering drug production
- Detection of drug production sites
The security industry is complicated by the need to balance the security of people with respect to the extent of preventive actions. After the 9/11 attack in 2001, Europe has experienced tragic attacks by terrorists (Madrid 2004, London 2005, and Oslo 2011) to mention a few involving the use of homemade bombs. An important question that follows concerns the amount of funds to be allocated to ensure the safety of the European citizens, and the world at large. During the course of the seventh framework programme, the European Union has invested a large amount of money in order to boost the relatively new and complicated research area called “Security of Explosives”. It is complicated in the sense that terrorists must not know what the possible counter measures are. This is one very important fact that makes classification of information necessary within this area. A cost-effectiveness study has been carried out in the project with focus on the EMPHASIS system where parameters such as e.g. equipment and staff training costs, installation and lifetime of components have been considered. The possible deployment of the EMPHASIS tools has been studied taking into account a few different scenarios in an urban environment. Furthermore, the public acceptance and legal framework has also been evaluated for the view of understanding how a system such as EMPHASIS can be used as a future security measure.
The development efforts made in the project have been communicated in several ways during the project. EMPHASIS information has been distributed via the EMPHASIS public website, by the participation in public media such as BBC world, radio and TV, in Swedish public media and in a number of newspapers and websites, e.g. New Scientist, Foxbusiness, CBS news and Dailymail and by taking part in scientific conferences. Furthermore, in the project a number of written reports with various dissemination levels (classified and public) have described the research progress continuously during the project.
Going back to the call ”Improving the security of the citizens” there is no doubt that the EMPHASIS system has the potential to improve the security of citizens. The project has shown that it is possible to locate illicit production of certain chemicals, within a sufficient timeframe. There are several ways of operating the EMPHASIS system. It may be used as a continuously monitoring system or as a reactive system used when suspicions, or needs, arise. The central server and client computer may easily be integrated into existing control/supervision centers and the communication channels are already in place.
The short-term potential impact depends on some factors; building sensors for daily use without costly maintenance, ensuring that the substance(s) detected matches the substance(s) of interest and a pronounced demand from one or several end-user.
In the long-term the EMPHASIS system has a large potential. Since the infrastructure needed is in place in most countries the main factor driving widespread use relates to the cost, performance and deployment of the sensors.
Sensor deployment depend mainly on size and power consumption, both of these factors are driven by technology development and volume production. Already today some of the components constituting the sensors are off-the shelf products. Within some years of technology development a sensor may be even more compact and possibly within a ten-year period it could be foreseeable that a sensor may be a medium-cost unit. Performance-wise, the sensors will benefit from the current miniaturization of electronics and optoelectronics which can enable enhanced detection of multiple substances in one single sensor as well as increased sensing performance.
No doubt, the potential applications of the EMPHASIS system will increase when sensors may be deployed in large numbers and can detect a multitude of substances. These applications will not only include localization of illicit manufacturing of different chemicals, but also detection of environmental hazards and long-term environmental monitoring. The system may also serve to generate statistics of chemicals present in the environment and generate data for the research community. As with many other systems, applications will pop-up once the capability is in place.
From a security perspective a geographically distributed EMPHASIS system may also aid and facilitate cooperation between nations in security and anti-terrorist matters. The various uses of the system may also facilitate cost-sharing between different end-users.
In summary, the performance and the successful use of a system such as EMPHASIS depends mainly on the type of sensors used in the system. It is the detection performance that is the most critical factor if a threat substance can be detected or not. If the needed detection capability exists then other factors will also influence the final result.
For detection in the vapor phase, the IR spectroscopic subsystem is at a level where it can be foreseen to be used in a real scenario for certain chemicals since it has the required sensitivity, selectivity, speed of detection and size of subsystem components. For the Raman spectroscopic subsystem, it has from the view of using the Raman based principle potential in the future for use in a system of the EMPHASIS type in terms of sensitivity and selectivity, however, much more technology development are needed for different components of the system in order to realize a dimensionally smaller system with also better sensitivity, ease of use and cost effectiveness.
The ion selective electrodes used in the project have been valuable in the research and have enabled to prove the viable concept of EMPHASIS for the detection of precursors in sewage. The sensor technique as such needs however to be developed much further in order to enhance parameters such as sensitivity and selectivity of the technique. This is required in order to realize these types of sensors in a system of the EMPHASIS type. Probably, other sensor techniques based on other detection principles will be of larger interest in the long term perspective.
For the detection of traces of explosives or precursors on different surfaces, both the IR and Raman based techniques are considered as having adequate sensitivities and selectivity’s. It will be of advantage in the further development work to enhance specifically the sensitivity but also the range of compounds that can be detected. In terms of cost effectiveness, the components building up the subsystems will hopefully be smaller and less expensive and this will be of importance for end users if commercialization of the tools is considered. The advances in the field of optical components are generally progressing fast and the future outcome will be of importance to follow from an explosive detection point of view.
If an EMPHASIS system had been existing 2005 and had been put into operation before the London bombings, the Leeds bomb factory might have been discovered. Consequently, this would have offered police forces the possibility to intervene and catch the terrorists at an early stage of the terrorist activities. This would then have stopped the attack and many lives would have been saved.
