EMPHASIS D5.1 Area monitoring optical system - FOI · PDF fileReport on area monitoring...

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EUROPEAN COMMISSION

Date:2012-11-05 Project No: 261381

FOI designation no: FOI-2009-1764 Dissemination Level: PU

Total No of pages: 17

Funding has been received from the European Commission’s Seventh Framework Programme (2007-2013)

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D5.1 Report on area monitoring optical system

Erwan Normand (Cascade Technologies), Ida Johansson (FOI), Krzysztof Młynarczyk (VIGO)

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D5.1 Report on area monitoring optical system

Due date of deliverable: 2012-09-30 Actual submission date: 2012-11-05 Version: 1.0 FOI designation no: FOI-2009-1764 Responsible: Erwan Normand (Cascade Technologies) Author(s): Erwan Normand (Cascade Technologies), Ida Johansson (FOI), Krzysztof Młynarczyk (VIGO) Number of pages: 13 Dissemination level: Public Start date of project: October 1, 2011 Duration: 3 years

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ContentContent ....................................................................................................................................... 3 1. Summary ............................................................................................................................ 4 2. Introduction ........................................................................................................................ 4 3. Context of the air‐monitoring subsystem of Emphasis ...................................................... 5 4. Air‐monitoring subsystem objectives ................................................................................ 5 5. Status of work, progress and achievements ...................................................................... 5 5.1 Quantum cascade lasers based infrared gas sensor (Air monitoring subsystem 1) ... 5 5.1.1 Compound characterisation and fingerprinting..................................................... 5 5.1.2 Laser wavelength selection .................................................................................... 6 5.1.3 Initial testing ........................................................................................................... 6 5.1.4 Sensor configuration .............................................................................................. 7 5.1.5 Sensor operation overview .................................................................................... 8 5.2 Sensor orthogonal data processing for the air monitoring subsystem ....................... 8 5.3 Sensor optical transceiver and receiver ...................................................................... 9 5.4 Sensor quadrant detector ......................................................................................... 10 5.5 Resonant Raman Sensor ............................................................................................ 11 5.5.1 Measurement wavelength interval ...................................................................... 12 5.5.2 Compound characterisation and fingerprinting................................................... 12 5.5.3 Sensor configuration ............................................................................................ 14 5.5.4 Sensor operation overview .................................................................................. 14 5.5.5 Initial testing ......................................................................................................... 15

6. Work progress summary .................................................................................................. 15 7. Planned future work ......................................................................................................... 16

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1. Summary This document is the report on area monitoring optical system of the Emphasis project at month 12. The objective of the EMPHASIS project is to test a system concept for detecting ongoing illicit production of explosives and improvised explosive devices (IEDs) in urban areas. It is aimed at narrowing down the search area in order for pin-pointing bomb-factories.

2. Introduction 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 vapour phase will be used. Multiple static sensors, positioned in the sewer, for the monitoring of the sewage for indicative traces will also be used. The detectors will be connected in a network and the total gathered data will be fused and evaluated in a command centre. Figure 1 depicts the concept for EMPHASIS.

Figure 1. The EMPHASIS concept.

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3. Contextoftheair‐monitoringsubsystemofEmphasis In EMPHASIS, the focus for the detection will be on three types of cases: a. Detection of explosives/precursors in vapour phase at low concentrations b. Detection of explosives/precursors at low concentrations in sewage. c. Detection of particles (low concentrations) e.g. door-handles or other covered surface. The fusion of sensor data achieved in the information handling part of the project will lead to potential alerts. The air-monitoring subsystem of EMPHASIS is concerned with the detection of explosives and precursors in the vapour phase at low concentrations.

4. Air‐monitoringsubsystemobjectives The aim of this work package is to generate, test and demonstrate an air monitoring subsystem for the detection of explosives and precursors in vapour phase. The system is based on rapidly chirped quantum cascade lasers operating in atmospheric micro-windows, advanced infra-red detector technology and Resonance Raman backscattering spectroscopy.

5. Statusofwork,progressandachievements

5.1 Quantumcascadelasersbasedinfraredgassensor(Airmonitoringsubsystem1)

To date, the works relating to the Air Monitoring Subsystem 1 (chirped quantum cascade lasers based on infrared gas sensor technology) has resulted in the characterisation, fingerprinting and test of 6 target compounds. Modelling and design of the Cascade TX/RX collection optics has been done allowing a detector system specification to be finalised. The development of the core detection engine of the system based on the Cascade CT3000 has been started and is on-going.

5.1.1 Compoundcharacterisationandfingerprinting During this work, Cascade has used its high resolution Fourier Transform Spectrometer (Bruker IFS 125) to characterise compounds of interest in the mid infrared region. This particular activity has led to:

• Molecule fingerprinting and sensor database creation • Selection of ideal wavelengths for carrying out the detection within the sensor

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Three examples are shown below in the figure 2 below.

Figure 2

5.1.2 Laserwavelengthselection Following the compound fingerprinting a detailed compound list was created. This work has been reported in the project “Threat and requirements analysis and detection strategy” and is part of a classified deliverable.

5.1.3 Initialtesting The detection was tested on exemple compounds in a long optical path cell configuration to assess the potential limit of detection (LOD/ppb.m). The tests showed the following results in term of limit of detection.

• Peroxide (~300ppb.m) • Ammonia and Nitric Acid (~100ppb.m) • Nitric Acid and Nitro methane (<100ppb.m)

During the operation the sensor Open Path LOD can be estimated as a function of plume size. The relevance of the compound LOD with the end user requirements has been reported in the earlier FP7 project LOTUS and will also be checked later in the EMPHASIS project on various compounds that are of relevance for illegal HME manufacturing. The graphs of figure 3 below show typical concentration spikes in pbb versus time within optical test cell, demonstrating the fast response of the sensor when the vapour of interest is present.

Hydrogen peroxide Nitric acid Ammonia Hydrogen peroxide Nitric acid Ammonia

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Figure 3. Typical spectra in optical test cell of the QCL IR based air-monitoring system.

5.1.4 Sensorconfiguration The Quantum cascade lasers based on infrared gas sensor technology (Air monitoring subsystem 1) will operate in an open path optical configuration of hundred meters of length with the signal reflected back from retro reflectors. The system concept is shown below in figure 4.

100-400m

Figure 4. Principle for the deployment of the QCL IR absorption technology in EMPHASIS for detection of precursor vapour plumes originated from illicit HME manufacturing. Cascade has started to build and assembly prototypes based on the Cascade model CT3000 OEM core engine. 4 lasers positions are currently available on this platform giving a detection capability of 5 to 7 compounds depending on priorities. The sensor is based on Quantum Cascade Lasers (QCL) operating in ultra fast chirped mode (scanning micro windows). The sensor will have a simple and user friendly human machine interface (HMI) using the Cascade model GS3. The CT3000 API has been adapted to be compatible with previous CT2000 used in the earlier FP7 research project LOTUS for detection of hydrogen peroxide vapours. The CT3000 core detection engine is shown in Figure 5.

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Figure 5. The Cascade model CT3000 core detection engine.

5.1.5 Sensoroperationoverview The sensor will be deployed on the roof of an infrastructure and the retro reflector will be deployed on the roof of a neighbouring infrastructure 100-400m apart. The IR beams of the sensors will be directed towards the retro reflector. The returned beams are collected and focussed onto a quadrant detector to maintain stable alignment and carry out the detection. The retuned beam is analysed by the sensor to reveal the chemical contents of the air between the sensor and the retro reflector. If a compound of interest (on board the sensor database) is fingerprinted, data is transferred to the EMPHASIS central system and evaluated if an alarm should be triggered or not. The type of compound, concentration of compound and position of the measurement will be part of the data package that reaches the EMPHASIS command centre.

5.2 Sensororthogonaldataprocessingfortheairmonitoringsubsystem

Within the work of the air-monitoring subsystem, the spatial and spectroscopic data from both Resonant Raman spectroscopic measurements and the measurements from active QCL spectroscopy will be combined in order to improve the receiver operating characteristics of the air monitoring subsystem. This novel combination of orthogonal spectroscopic selection rules and strengths of each technique will result in an improved probability of detection and a reduction of false positives. The output form this work feeds into Information management and data fusion. The result is an increased user assurance which is important for the Cost effectiveness carried out in other parts of the project.

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With respect to the Air monitoring subsystem developed by Cascade (CT3000 active QCL spectroscopy) its API will be compatible with previous CT2000 used under LOTUS.

5.3 Sensoropticaltransceiverandreceiver The air monitoring subsystem 1 will operate in an open path optical configuration of hundreds of meter in length with signal backscattered from retro reflectors. The sensor is equiped with an optical transceiver (TX) and a receiver (RX) having the following features (optical modelling shown in figure 6): Optical TX

• 4 distinct wavelengths are collimated and co aligned in the sensor • The wavelength range is 8-12µm • TX expends the output beam so that the power is eye safe • The IR beam are invisible and are therefore covert • Aspheric optics for low divergence are used to ensure 100-400m open path • The divergence will be in the order of 2mRad

Optical RX

• The returned beams are collected via single lens • The collected light is directed to quadrant detector • Quadrant detector provides data to actively correct system alignment and carry out

detection The development of the suitable all weather TX/RX optics is underway and based on initial optical modelling (see figure 6). The air monitoring subsystem 1 will be all weather functioning using a retro reflector. The initial model is developed and enables to establish the detector system specification. The model has been incorporated into ZEMAX optical modelling tool for assessment by Cascade and Vigo for the detector system.

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Optical TX Optical RX Figure 6. Principle for the transmission and receiver functions.

5.4 Sensorquadrantdetector The UK SME Cascade is working with the polish SME Vigo in order to enhance the current detector noise level and improve the signal to noise ratio and beam pointing stability. The detector specification indentified is suitable for 0.1% signal return (tested in model). The detector takes the form of a quadrant detector arrays to allow active X/Y steering of the optical TX/RX optics with respect to the retro reflectors insuring constant alignment and optimum signal strength (model shown in figure 7). The key features of the quadrant detector are listed below:

• System returned power has been modelled at 0.1% (0.5mW from 500mW peak) • The detector technology is based on room temperature MCT photoconductive detector

(PCQI) in a quadrant arrangement of 4x(1x1 mm) • The detector is stabilised in temperature by a 3 stage peltier element • Immersed optics increase responses

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Figure 7. Specification and outline of the quadrant detector.

5.5 ResonantRamanSensor The Air Monitoring Subsystem 2, based on Resonance enhanced Raman spectroscopy, will be developed and demonstrated during the project. The sensor is the first of its kind, and will be used to show proof of principle for that Resonance Raman spectroscopy can be used for stand-off detection of explosives vapours and hence of illicit explosives production. Until date, a first version of the setup has been made, with specially bought items to maximize the transmission of the system. Target compounds for initial measurements have been selected and characterized.

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5.5.1 Measurementwavelengthinterval The Resonance Raman sensor requires a tuneable laser, to match the applied laser wavelengths with the resonance wavelengths for the threat substance being searched for. A tuneable filter is also needed, to suppress the signal from backscattered laser light. FOI has got a laser that is custom built to be continuously tuneable from 2300 nm down to 195 nm. Tuneable filters are today however not yet available in the deep UV, where most explosives undergo resonance. The filters of today can be used down to approximately 320 nm, and experiments will therefore be made in this wavelength range initially. For this purpose, substances with resonance wavelengths in the same region will be used. If filters cannot be obtained in the deep UV, measurements can carefully be attempted without filters, later on in the project.

5.5.2 Compoundcharacterisationandfingerprinting In order to characterize the selected target compounds, different types of spectra have been measured:

• UV absorption spectra • Reference Raman spectra • Resonance Raman spectra on solutions at close range stand-off distances

UV absorption spectra of selected target compounds have been measured, in order to identify possible resonance wavelengths. The wavelength of maximum resonance is expected to coincide approximately with an absorption maximum. The UV absorption spectra are shown in figure 8 below, where the blue field marks the wavelength range where tuneable filters are available.

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High resolution reference Raman spectra were acquired for the selected target compounds using a table top FTIR/Raman spectrometer (Bruker IFS 55 with FRA 106 Raman module). The instrument uses a continuous Nd:YAG laser operating at 1064 nm. Reference spectra and resonance spectra differ however, since they are measured at different wavelengths; during resonance, different Raman lines are resonance enhanced to different extent. In order to determine the resonance behaviour for the different substances, Raman spectra were measured on solutions at close range stand-off distances, in the setup shown in figure 9, using the tuneable laser and filter. 4-nitrophenol showed the highest resonance enhancement in the wavelength interval of the measurements, the resonance spectrum and the wavelength dependence of the enhancement being shown in figure 10.

Figure 9. The setup for close range measurements of Resonance Raman spectra on solutions,

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Figure 8. Absorption spectra for selected target compounds. The blue field show the wavelength range were tunable filters are available.

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Raman shift (cm-1)

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Figure 10. Left: Resonance Raman spectrum of 4-nitrophenol solved in acetonitrile, 1g/l, measured at 321 nm (above). Red arrows indicate peaks of 4-nitrophenol. Comparison is made to the spectrum of pure acetonitrile at 321 nm (middle) and the reference spectrum of pure 4-nitrophenol measured at 1064 nm (below). Right: the wavelength dependence of the signal intensity from the 1326 cm-1 peak in 4-nitrophenol.

5.5.3 Sensorconfiguration The Resonance Raman system (Air monitoring subsystem 2) will operate in an optical open path configuration of approximately up to one hundred meters. The horizontal and vertical angle from the sensor to the target area can be selected, as well as the distance. The system will hence be able to determine location and spatial distribution of the target substance vapour.

5.5.4 Sensoroperationoverview The system is intended to be used on the roof of an infrastructure and measure the surrounding air space up to a hundred meters from the sensor. The laser beam from the sensor illuminates the target area, and scattered light is collected by a telescope in a coaxial setup. Backscattered light of the laser wavelength is removed by a tuneable filter while the collected Raman light is passed to a spectrograph and spectra are registered by a gated ICCD camera. The spectrum is analysed and, if a compound of interest (within the sensor database) is detected, data is transferred to the EMPHASIS central system and it is evaluated if an alarm should be triggered or not. The measurement is then repeated for laser wavelengths corresponding to resonance wavelengths of all compounds of interest. The type of compound,

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position of the measurements and spreading of the compound will be part of the data package that reaches the EMPHASIS command centre. The FOI system, which is a first laboratory prototype, will for the demonstration be mounted on a stationary optical table. The angles to the target area will be selected by steering a motorized mirror mount within the system. The distance to the detection volume is determined by gating the ICCD camera. The path length of the measured target volume will be approximately 2 meters, with the laser pulse length being 6 nanoseconds.

5.5.5 Initialtesting FOI has built a first setup for measuring on vapours, with the setup positioned in a laboratory adjacent to a test field, where explosives can be handled and vapours can be released. The setup has not yet been used for vapour measurements, and optimization of the setup remains. There have been some delays in the experimental work due to problems with equipment; a spectrometer has been away for reparations during the main part of the year. Measurements will be continued during the remaining time of the year and during next year. Close range stand-off measurements confirm that the selected target substances will undergo resonance in the wavelength interval where initial testing will be made, and they should therefore be suitable for the measurements.

6. Workprogresssummary Resonant Raman Spectroscopy

• Target compounds for initial measurements have been selected and characterized • A first version of the setup has been made

Active QCL transmission spectroscopy

• Laser wavelengths selection established for 6 compounds • IR fitting algorithm development initially tested for detection • The sensor will have a simple user friendly human machine interface (HMI) using

GS3 • CT3000 API has been adapted to be compatible with previous CT2000 used under

LOTUS (Portendo) – task under workpackage 7

Sensor orthogonal data processing • An orthogonal data processing activity (WE5.3) supports workpackage 7 and

workpackage 7. Air monitoring subsystem 1 and 2 will communicate with a LOTUS compatible API (developed by Portendo in workpackage 7).

Optical system configuration

• The development of a suitable all weather TX/RX optics is ongoing

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• The air monitoring subsystem 1 will be all weather using retro reflectors • Initial optical model developed and currently being prototyped

Detector system adaption

• Vigo is working with Cascade to enhance the current detector noise level and improve signal to noise ratio

• Initial detector specification indentified suitable for 0.1% signal return • The detector also takes the form of a quadrant detector arrays to allow active X/Y

steering of the optical TX/RX optics with respect to the retro reflectors insuring constant alignment and optimum signal strength

• Initial model incorporated into ZEMAX optical model and assessed by Cascade and Vigo

• First prototype delivered to Cascade

7. Plannedfuturework It anticipated that towards the end of the first half of 2013, the air-monitoring subsystem based on the QCL IR absorption technology will be tested in the field at the test site of Swedish Defence Research Agency. The tests will be carried out outdoors and measurements of explosives and precursors to explosives in the vapour phase will be measured. The target vapours will be studied outdoors from an indoor production of HME. The scenarios in question have been decided in the threat and analysis requirements section of the project. The measurements will reveal important information for the system such as system capacity and range of targets to be detected. The data will feed the part of the project that address data fusion and alarm resolution. The advantage of the study is that it will be tested in the field, at an all-fenced and controlled test site where real manufacturing of HME will be performed. In this way it will be as close to a real situation as possible. The results will be reported later in the project at classified level.

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EMPHASIS is a collaboration between: FOI | TNO | Fraunhofer ICT | Fraunhofer IAF | Portendo | Cascede Technologies | MORPHO | Institut National de Police Scientifique | VIGO |

Coordinator Website FOI, Swedish Defence Research Agency www.emphasis-fp7.eu Department of Energetic Materials Grindsjön Research Centre SE-147 25 Tumba SWEDEN

EMPHASIS has received funding from the European Commission’s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No 261381

The objective with the EMPHASIS project is to develop a system for detecting ongoing illicit production of explosives and improvised explosive devices (IEDs) in urban areas. The EMPHASIS system will be composed of networked sensors. Area sensors, strategically positioned, for the monitoring of explosives or precursors to explosives in the vapour phase will be used. Static sensors, positioned in the sewer, for the monitoring of the sewage for indicative traces will also be used. The detectors will be connected in a network and the total gathered data will be fused and evaluated. If a threat substance is detected in elevated amounts, information about the type, location, time and amount will be registered and sent to a command central where further evaluation and appropriate actions can be initiated. The intention is to cover a large area that can be reduced step by step into narrower areas due to a positive alert. The number of sensors used will be increased in the smaller areas. For the final verification stand-off detectors in equipped mobile units will be used to pinpoint the location of the bomb factory. The techniques adopted in the project include electrochemical sensors for the sewage subsystem, resonant Raman and active QCL (Quantum Cascade Laser) transmission spectroscopic techniques for the area monitoring subsystem. Active imaging IR (Infra Red) laser backscattering and stand-off imaging Raman spectroscopic techniques will be used in the final verification. In the EMPHASIS project, threat analysis and search strategy, system network and integration, deployment, legal aspects, cost effectiveness and data fusion and information management will be evaluated. The project also includes a test and subsystem validation part. The consortium consists of eight partners, research institutes, an industry, SMEs and an end user.

EMPHASIS D5.1 Area monitoring optical system - FOI · PDF fileReport on area monitoring...

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