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1. 2 Graph oi 1 Graph 6 0 Amplitude OPEB n 1130 0 1200 0 1300 0 Wavenumberfcm 1 0 0 1 D i 7 1130 0 1200 0 1300 0 1420 0 Wiavenumberfcm 1 2 1 Graph Amplitude v oO un 1 1 1 1250 00 1300 00 1350 00 Wavenumbertcm 1 1 1200 00 0 00 i 1131 00 SE 1420 0 i 1 1420 00 Test Result Profile path g C LPAS_Single Profile p5_so profile txt File path 4 C LPAS_Single Profile p5_so acet1 txt Plot O 1222 9 0 6 Dips_VYvaveNo 1222 9 0 Intensity 0 1 Fae eo Zoom 3 1 length JE Scale Max A J Y Scale Min F o Cursors Plot O j 1259 2 1280 4 1308 5 j 1330 8 1357 5 o fosce fase fore a a o o E Dip Cal Explosive Hazardous Chemical Intensity Wavenumber 0 1 1222 9 x iy 1222 92 0 10 Ty new _paperl Compet Figure 5a Test Result GUI showing detection of acetone in liquid form from diffused aluminium surface Laser Current internal external internal used for alignment purposes external It is used when laser is modulated by a pulse waveform generated by function generator module for the detection of explosives Laser wave number as per the frequency range of the laser head Laser Scan settings Start position Stop position Scan rate Step size Scan Mode Forward Sweep Automatic Scan Forward
2. Journal of Lasers Optics amp Photonics Sharma et al J Laser Opt Photonics 2014 1 2 http dx doi org 10 4172 jlop 1000109 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System Ramesh C Sharma Gupta S Deepak K Sanchit G and Chandra H Laser Science amp Technology Centre DRDO Delhi India Abstract This paper focuses on the design and development of measurement technique and processing of signal for the detection of various explosive simulants like RDX cyclo trimethylene tri nitramine TNT Trinitro toluene Sarin TATP Tri acetone triperoxide their simulants like nitrobenzene DNT Dinitro toluene DMMP DiMethyl Methyl Phosphonate acetone propanol etc in different states of matter adsorbed on a metallic surface from a standoff distance ranging from few meters up to a distance of 25 meters in the wavelength range of 7 9 um The focus also lies on the measurement methodologies and the instrumentation employed in these systems A dedicated single screen single user user friendly Graphical User Interface GUI for controlling the entire system acquisition and processing of the incoming signal and demonstration of results has been developed with the help of Laboratory Virtual Instrument Engineering Workbench LABVIEW The dual phase sensitive detection technique has been employed The Data Acquisition for Explosive Detection System DAEDS also carries out precise operation sequ
3. 0 90 Zoom E 7 g 080 m Explosive Hazardous eng 3 2 0 70 ar Chemical lt L x E m 0 60 Scale Max 0 50 1 5 0 40 Intensity Wavenumber 0 30 K Scale Min 0 52 1213 9 a a a 0 20 i 0 00 l l l l l l 1 1131 00 1200 00 1250 00 1300 00 1350 00 1420 00 wWwavenumbericm 1 Y1 Graph YTZ Graph eS r 3 0 Profile path 7 CALPAS_ Single Profile p10_so profile ctHt 4 25 i Iae File path 3 0 eee q CALPAS_ Single Profile p10_so dmmpi1 tHt E pk Saee Seg 2 0 lt L Gom 1 5 1 0 Select Profile 1 0 0 5 0 5 00 1 Tete nee ery 00 i I 7 1 ol i 1130 0 1200 0 1300 0 1420 0 1130 0 1200 0 1300 0 1420 0 Piot O 1247 0 0 4 ao D E Hiten ity wavenumbericrm i j Wavenumbertcm 1 1247 z 0 jo 124 2 1 Graph 1288 8 Jozi 1298 2 Jossa Ji304 5 0 631 1320 1 10 543 1342 9 1 014 o Zoom SE F E Explosive Hazardous eng a arz Chemical Y Y Scale Max 1 5 n Intensity Wavenumber 0 12 1247 Y Scale Min Ell ce Cursors 1 I I I I 1 I I 1131 00 1200 00 1250 00 1300 00 1350 00 i420 00 Wiavenumbertcm 1 Figure 5d Test Result GUI showing detection of DMMP in liquid phase on diffused aluminum surface J Laser Opt Photonics ISSN JLOP an open access journal NOU severe IONS Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade
4. and Reverse Sweep number of scans to be done After setting the laser parameters the laser is sent to the target The laser is interfaced with the computer through laser controller 3 4 5 6 The graph on the main screen shows the laser profile on the target A provision of the Next Run as shown in the GUI is made if two or more graphs are required to be seen on the same screen This helps in comparison of two or more graphs All the profiles viz laser profile explosive profile are stored separately in a file They can be compared and after comparison the type of the explosive can be detected A library of various explosive has been made and stored in the computer through which the profiles of the different explosives chemical agents can be compared and then detected A multifunction Data Acquisition Card USB 4716 has been utilized for measuring the incoming signal 12 This multifunction card is USB compatible and can be connected to the computer through a USB cable It also offers the advantage J Laser Opt Photonics ISSN JLOP an open access journal Volume 1 Issue 2 1000109 Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 Page 5 of 8 of having digital input channels digital output channels and analog output channels It offers 16 sin
5. 009 ARL TR 4782 US Army Research Lab 3 Sharma RC Kumar D Bhardwaj N Chandra H Maini A K 2013 Portable detection system for standoff sensing of explosives and hazardous materials Optics Communication 309 44 49 4 Van Neste CW Senesac LR Thundat T 2009 Standoff Spectroscopy of Surface Adsorbed Chemicals Analytical Chemistry 81 1952 1956 5 Pohlkotter A Willer U Bauer C Schade W 2009 Resonant tuning fork detector for electromagnetic radiation Applied Optics 48 119 125 6 Barbic M Eliason L Ranshaw J 2007 Femto Newton force sensitivity quartz tuning fork sensor Sensors and Actuators A 136 564 566 7 AD829 High Speed Low Noise Video Op Amp Data Sheet 2014 8 D11 00002 01 REV A Tunable laser system user manual 9 DO9 00002 01 REV A User Commands Mid IR External cavity Laser System 10 MODEL SR830 DSP Lock In Amplifier Manual Rev 2 5 2011 11 LABVIEW user manual 1998 12 Multifunction Data Acquisition Card USB 4716 user manual 2014 Submit your next manuscript and get advantages of OMICS Group submissions Unique features e User friendly feasible website translation of your paper to 50 world s leading languages e Audio Version of published paper e Digital articles to share and explore Special features 350 Open Access Journals 30 000 editorial team 21 days rapid review process Quality and quick editorial review and publication processing Indexing at Pu
6. 1249 4 1323 1 1359 41 a A Een EA 0 0 0 Explosive Hazardous Chemical IntensityWavenumber 0 14 1359 5 Cursors x AY 1450 00 1359 4 O 1 lt l l I 1 1250 00 1300 00 1350 00 1400 00 Plot 0 Wavenumber cm 1 Laser_Controller lyproj My Computer start Pegasus Laser_Controller lvpr Microsoft PowerPoint Figure 5f Test Result GUI showing detection of Nitrobenzene in liquid form from diffused aluminium surface J Laser Opt Photonics ISSN JLOP an open access journal Volume 1 Issue 2 1000109 Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 can be changed as per the intensity of the incoming signal The software has been designed in such a way that a change in the value of dip position within a particular range does not affect the detection of the explosive materials These ranges are user defined and are different for different explosive materials The lock in amplifier function generator Quantum Cascade Laser etc are controlled through the data acquisition system Moreover whole system is user friendly and controlled through a single screen GUI and by a single user We have successfully developed a trolley mounted movable engineering prototype system which is capable of detecting explosives chemic
7. Laser Photoacoustic Spectroscopy based Explosive Detection System Y1 Graph 6 0 5 0 Ea w Intensity v N 0 0 0 I 1 1130 0 1200 0 1300 0 Wavenumber cm 1 J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 Page 7 of 8 2 Graph SHES 4 C ishl_TestData Test Result fice Cursors ia BACK ma ereed Plot 0 1392 1 2 0 3 0 2 5 ee 1 5 1 0 Dips_WayveNo 1187 8 2o mhas Intensity l 0 5728 0 5665 0 0 1 I 1130 0 1200 0 1300 0 Wavenumber cm 1 W DE 1420 0 1420 0 Cursors x l Y ea Plot 0 1392 1 0 6 Intensity v 0 00 z I I 1100 00 1150 00 J 1200 00 Laser_Controller lyproj My Computer a Start G Pegasus 0 0 I 1 1130 0 1200 0 1300 0 Wavenumber cm 1 TT 1420 0 faas Em 10 5355 0 3841 0 4279 0 289 0 0 Explosive Hazardous Chemical IntensityWavenumber par 0 26 1392 1 1450 00 1392 07 0 2 I I 1 I 1250 00 1300 00 1350 00 1400 00 Wavenumber cm 1 Plot 0 Laser_Controller lvpr 2 Graph zG eaol Test Resu Iit ile path 4 C Vishl_TestData o Ba Plot 0 1359 5 2 1 Dips_WayeNo i l i uo Intensity y m i o 5 Intensity Jo 1190 4 Jo 10 5915 1203 3 Cursors x AY 1359 5 0 3 0 0 I 1 1130 0 1200 0 1300 0 Wavenumber cm 1 og 1420 0 Plot 0 0 5794 0 00 l 1100 00 l I 1150 00 1200 00 1224 9
8. Page 3 of 8 xY Graph 5 5 5 0 Amplitude o 0 RA Re 1 BI 220 868 18 LAN a Ke ad BN ol by AY De aS el AC a AA A A i VRE Sat ma an ON at A A I LA Sa kor AD Sel det RA OA i I AEA St i ira Del FM i 1130 0 1200 0 1250 0 1300 0 1350 0 1400 0 1450 WaveNumber cm 1 Done Press Next Next Run Graph Reset Cursors xX iY 1215 7 0 7 W untitled Paint On Screen Keyboard me newapp_standoff E gt PEGASUS vi 10 59 AM Figure 3 Single screen GUI frequency of interest AD829 based pre amplifier was fabricated in the trans impedance mode as shown in Figure 2 Tunable laser The Tunable Laser System consists of a Laser Controller a tunable Laser Head and an umbilical cable assembly 7 The purpose of the laser system is to provide tunable mid IR pulsed laser radiation over a specified tuning range The system provides laser Tunability temperature control and laser current control The laser controller is interfaced with the Computer through any one of the Controller s data ports viz USB port GPIB port or RS232 port Upon power up the Controller automatically interrogates the Laser Head to determine its center frequency tuning range and other Laser Head specific information All this information is returned by the laser to the controller which in turn can be viewed on to the computer 8 All the parameters of the laser viz laser scan rate scan range number of scan
9. T Te _ Cursors x iy Plot O 1374 7 O 7 see mon rue Ope enc Dips_WaveNo fizera So j1z70 1320 1 Cursors Intensity Tert TENES TECTA soa fone Pose ETEN Jo 124 1391 4 0 174 D o Plot O 1227 4 0 9 a 1370 3 j 1377 3 Zoom J a Explosive Hazardous Chemical EE J Intensity Wavenumber Y Scale Min afo 0 15 1227 4 length pa Cursors i Si Corsa l Plot 0 1227 35 0 15 Figure 5b Test Result GUI showing detection of acetone in vapour phase J Laser Opt Photonics ISSN JLOP an open access journal Volume 1 Issue 2 1000109 Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 Page 6 of 8 1 Graph 2 Graph 5 0 Profile path 9 C LP45_Single Profile pl4_so profile txt 5 0 File path 4 0 ae SES 9 C LP45_Single Profile pi4_so dnt264 txHt 3 0 5 30 mB an Plot O 1374 7 0 7 F zo Cursors ix dif E LUFO 0 0 l l 1 o 0 RSA Soar 1130 0 1200 0 1300 0 1420 0 1130 0 1200 0 1300 0 1420 0 Wayenumbertcm 1 4 Wavenumbertcm 1 4 Dips_WaveNo Intensity 2 41 Graph 1269 8 0 796 ciate 1319 6 0 995 1342 6 11 115 PEA 1390 8 1 907 1401 6 11 728 T nh
10. als in trace amounts without using sample collection step and from safe standoff distances This system is capable of detecting the explosives chemicals with concentration of the order of 100 nl in liquid 1 0 ug cm explosive simulants at adsorbed surface and 1 0 ppm in vapor phase from a safe standoff distance ranging from few meters up to 20 meter The experimentally determined absorbed wavelengths of above mentioned explosives chemicals are matching with the absorbed wavelengths as provided in the literature for the respective explosives chemicals This confirms the accuracy of our system Moreover the system is easy to use as it has a single screen GUI which is single user operable Presently we are working on miniaturization and automation of this system for development of a Tripod mounted system having increased sensitivity selectivity and target ranges Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 Page 8 of 8 Acknowledgement Authors are thankful to discuss of the present with Professors Thomas Thundat Alberta University Canada S N Thakur BHU J P Singh Mississippi State University USA References 1 Van Neste CW Senesac LR Thundat T 2008 Standoff photoacoustic spectroscopy Applied Physics Letters 92 234102 2 Gurton K Felton M Tober R 2
11. bMed partial Scopus EBSCO Index Copernicus and Google Scholar etc Sharing Option Social Networking Enabled Authors Reviewers and Editors rewarded with online Scientific Credits Better discount for your subsequent articles Submit your manuscript at http www omicsonline org submission J Laser Opt Photonics ISSN JLOP an open access journal Volume 1 Issue 2 1000109
12. encing parameter control parameter measurement and storage of data The incoming signal profile has been normalized with respect to the reference laser profile to obtain the resultant graph Various experiments have been conducted and the resultant graphs have been plotted with intensity on the y axis and wave number on the x axis as shown in the results section of this paper Furthermore online determination of the explosive or the simulant has been carried out An engineering proto type system has been developed which indicates the detected explosive simulant using the developed software Keywords DAEDS Dual phase sensitive detection lock in amplifier Hazardous chemicals and Explosive detection system Graphical User Interface LABVIEW Dual phase sensitive detection lock in amplifier Introduction Terrorists are regularly using new techniques for mass destruction against civilian population Therefore the detection of explosives from safe standoff distances is very important for countering the terror attacks as it involves innocent civilian population Keeping this in mind governments all over the world are encouraging programs for safe standoff detection of explosives This also enhances the economic growth of the nation These threats include potential release of hazardous chemicals biological warfare agents and explosives In order to neutralize the impact of such threats they require early detection from a safe standoff distance in
13. gle ended 8 differential analog input channels with 16 bit resolution 0 15 accuracy at full scale up to 200 kS s throughput over voltage protection 16 digital I O lines and 1 user counter and two 16 bit analog outputs It obtains all required power from the USB port so no external power connection is ever required 7 A trolley mounted prototype system has been developed as shown in Figure 4 in which all the opto electronic components including the laser pre amplifier the DAQ cards etc are mounted inside the metallic enclosure This trolley mounted prototype system can be taken to any place for testing of the explosives All the operation of the entire system can be conducted through a single screen GUI shown in Figure 4 Results and Discussions This section deals with the results and the necessary discussions Various graphs viz laser profile explosive profiles for the detection of Acetone Acetone in vapor form Propanol DNT DMMP and nitrobenzene are shown in Figure 5a 5f Initially the laser profile was recorded and then in the second run the explosive chemical profile was recorded The laser profile has to be recorded only once at the starting of the experiment Very frequent changes in the ambient atmospheric conditions in the near earth environment causes the laser profile to change Therefore it is compulsory to record laser profile every time we start an experiment This recorded laser profile can be utilized for detect
14. ion of different explosives The laser profile graph has been denoted as Y1 graph and the explosive profile graph has been denoted as Y2 graph Both these profiles were recorded and processed to obtain a software compatible profile for the detection of dips in efficient way This normalizes the explosive profile with reference laser profile to obtain the resultant graph and hence clearly indicates the dips that are l PostAnalysys3 vi generated because of the presence of explosive The target was kept at a distance of 20 m from the trolley mounted system The explosives chemicals have been detected in all the three states of matter The data obtained indicates repeatability The detection of hazardous materials has been performed by using both the online detection and the post processing methods The false alarm rate has been found out to be approximately 5 on the detected explosive materials The low false alarm rate indicates the very high accuracy of the developed data acquisition system Moreover the response time of the system is of the order of few milli seconds The data of the online detection was stored in various files for post detection analysis The dip position of the various explosive materials depends on various factors like atmospheric conditions distance of the target from the sensor characteristics of the explosive material Therefore the dip values lie within a certain band of 5 cm from a central value Therefore there i
15. isplay storage and analysis of parameters of QCL and various explosives chemical materials The data acquisition system successfully implements the requirements of sequential and switching control of laser output the online adjustment and display of parameters such as laser temperature laser wave number laser current laser scan rate laser scan start and end position and storage of these parameters The DAEDS successfully implements the diagnostics measurement of incoming signal intensity and online detection of explosive chemical present A user friendly single screen single user operable GUI as shown in Figure 3 was conceptualized and developed using LABVIEW which is used for operating the entire system 11 The PC based approach is selected because of the advantages of functionality and flexibility The main features of the DAEDS are as follows in Figure 3 1 The setting up of initial laser parameters and their finalization The following laser parameters requirement can be set as per the J Laser Opt Photonics ISSN JLOP an open access journal Volume 1 Issue 2 1000109 Citation a b Laser Pulse mode d 2 Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 Page 4 of 8 Figure 4 Trolley Mounted Prototype System PostAnalysys3 vi
16. otonics ISSN JLOP an open access journal Volume 1 Issue 2 1000109 Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 i PEGASUS vi 10 59 44 Technical Information Controller Modell 1001 TLC PEGASUS Software version Zii Controller Serial Number 253 Control Board Firmware Yersion C_4 2 1 11080 UT Motion Board Firmware Version M_3 1 0 Laser Head Model Laser Head Serial Number 11080 UT 015 Laser Hours of Operation 0 00 Laser Temperature Laser Output Current m 1250 lt J Puls Width us 0 50 Duty Cycle 5 0 Set Point deg C 15 00 Pulsing Puls Freg kHz 100 0 Pulse Mode external 4 gt 4 gt Pulse Period us 10 Trigger Delay ns 0 00 Laser Status T Head EE io Current Laser 4250 ma Current T Case MEEA ieo Fr EE Tuning Range 7 04225 to 8 84960 Range 1130 00 to 1420 00 um Wavelength um 7 84212 S Wavenumber cm 1 1130 00 scanning Start Position cm 1 1130 0 No of Scans 1 i Current Scan 1 Start Scan Forward Swee cm 1 P um Scan Mode End Position cm 1 1420 0 Scan Rate 1 4 gt 4 gt 40 4 gt Step Size 1 00 E Scan Status Scans Completed 2 1 Graph File path 94 C LPAS_Single Profile p13_so dnt264 txt
17. plosive detection system which shows the various electro optical components that are required for successful detection of the explosives chemicals etc In the following paragraphs different components are explained in detail shown in Figure 1 AD829 based pre amplifier circuit The AD829 based pre amplifier circuit is used for enhancing the amplitude of the incoming signal and converting the input current signal from the detector into voltage signal This output signal can read by the lock in amplifier The pre amplifier circuit consists of Quartz 0 4 pt 10 pt Tantalum Output L 10 pt T Hif ae aag v Crystal Tuning Fork QCTF detector 3 The detector is mounted on the PCB based pre amplifier circuit shown in Figure 2 The QCTF detector converts the incident optical energy into electrical energy in the form of current The resonant frequency of the QCTF based detector is of the order of 32 7 KHz with bandwidth of 4Hz As the current produced by the QCTF detector is of the order of nano amperes hence High Speed Low Noise Video Op Amp AD829 is employed The AD829 is a low noise 1 7 nV VHz high speed op amp has excellent gain has a slew rate of 230 V us and settling time of 90 ns to 0 1 Input Offset Drift of 0 3 uV C Moreover the feedback resistance has been taken to be variable so that gain of the pre amplifier can be changed as and when required Because of the above features of the AD829 at the J Laser Opt Ph
18. s step size can be controlled through a standard GPIB cable which in turn is connected to the computer Function generator Tektronix AFG3102 In the experiment dual channel function generator 9 is used to modulate the laser and also used by the lock in amplifier as a reference signal to lock on to the incoming signal from the PCB based pre amplifier It plays a very critical role in the experiment The most important criteria for the lock in amplifier to lock is that the frequency of both the channels of the dual channel function generator should be same as that of the resonant frequency of the QCTF based detector viz 32 7KHz Lock in Amplifier SR830 A lock in amplifier use a technique known as dual phase sensitive detection to single out the component of the signal at a specific reference frequency and phase and thus eliminates the phase dependency of the output signal of the lock in 10 The dual phase sensitive technique enables the lock in amplifier to be totally independent of the phase of the incoming signal The lock in amplifier locks the incoming signal with the reference frequency signal and rejects all the other noise frequencies Data acquisition for explosive detection hazardous chemicals system daeds daq A general purpose data acquisition system for explosive detection system DAEDS has been designed and developed to meet the real time requirements of operational control acquisition measurement monitoring d
19. s a slight change in the value of dip positions every time an experiment is conducted The software has been designed in such a way that a slight change of 5 cm in the wave number has been accounted for Moreover a zoon factor has been added in all the graphs for increasing the amplitude in all the graphs The total time taken for processing the information and for detection of hazard and displaying the hazard on the screen is less than 5 sec Figure 5 The LPAS signal is very high SNR at 20 meter distance In further experiments standoff LPAS will be demonstrated up to 50 meter Sensitivity also will be improve using the Laser power with modulated frequency of the QCTF detector Conclusion The DAQ system has been able to successfully demonstrate the detection of stimulants of explosives The gain of the AD829 based pre amplifier circuit can be modified just by changing the value of the variable feedback resistance In this way the output of the pre amplifier 2 Graph 3 5 gt 1 Graph 6 0 3 0 Amplitude y 0 7 1 1 res 1130 0 1200 0 1300 0 1420 0 Wavenumberfcm 1 I 1300 0 Wavenumberfcm 1 o o i 1130 0 1200 0 2 1 Graph Amplitude 0 00 1 i 1 1 1 1131 00 1350 00 1420 00 I 1300 00 Wavenumber cm 1 1 1 1200 00 1250 00 Test Result Profile path g C2 LPAS_Single Profile p14_so profile txt File path 4 C LPAS_Single Profile p14_so acevap txt ee e
20. tec drdo in Received August 26 2014 Accepted October 31 2014 Published November 10 2014 Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 Copyright 2014 Sharma RC et al This is an open access article distributed under the terms of the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original author and source are credited J Laser Opt Photonics ISSN JLOP an open access journal Volume 1 Issue 2 1000109 Citation Sharma RC Gupta S Deepak K Sanchit G Chandra H 2014 Standoff Quantum Cascade Laser Photoacoustic Spectroscopy based Explosive Detection System J Laser Opt Photonics 1 109 doi 10 4172 jlop 1000109 Page 2 of 8 BLOCK DIAGRAM OF STAND OFF EXPLOSIVE DETECTION TECHNOLOGY LPAS SYSTEM l i E m F a z kL T T EES oem Es me Ten ee E mae Detector Folding Mirrors neesten Rod eidi Oipilos Target E E i l l M l M Figure 1 Block diagram of standoff explosive detection system 1megqa ohm fixed in series With 1 mega ohm Variable Detector g H 15 W AD829 based Pre amplifier circuit Figure 2 AD829 based Pre amplifier Circuit Experimental System Design and Operation Figure 1 shows the block diagram of the standoff ex
21. the presence of ambient conditions With the development of high power miniaturized tunable Quantum Cascade lasers QCL the Quartz Enhanced Laser Photoacoustic Spectroscopy QE LPAS Technology has emerged as a powerful technique for standoff detection of explosives chemical agents This technique is an extension of conventional photo acoustic spectroscopy technique PAS 1 2 In this technique QCL source is modulated at the resonant frequency of Quartz Crystal Tuning Fork QCTF i e 32 8 KHz which acts as a detector and enables total insensitivity to ambient CW radiations Details of the technique are explained in reference 1 3 The main advantages of this technique is that it offers standoff detection of low concentration up to ppb level of chemicals explosives without using a sample collection step by the detection of trace quantities of surface adsorbed chemicals explosives 4 6 The main aim was to develop a stand alone single user operable single screen operable data acquisition system that could be sufficient is detecting the explosives from safe standoff distances In the present paper we have outlined the methodology for the design and development of Data Acquisition for Explosive Detection System DAEDS which is applicable for the detection of explosive materials like RDX cyclo trimethylene tri nitramine TNT Trinitro toluene Sarin TATP Tri acetone triperoxide and their simulants like nitrobenzene DNT Dinitro tol
22. uene DMMP Di Methyl Methyl Phosphonate acetone propanol etc in different states of matter adsorbed on a metallic surface from a standoff distance ranging from few meters up to a distance of 20 meters in the wavelength range of 7 9 um This paper also reports the manner in which LABVIEW along with DAQ cards have been utilized by DAEDS to obtain critical parametric results and optimization of system parameters This paper also presents Standoff QE LPAS spectrum of explosive simulants molecules adsorbed at diffused aluminum plate from a distance of up to 20 meters in different states of matter Experimentally we have developed a Trolley mounted portable system for detection of explosives In future with the increase in the power of QCL Laser due to technology advancement the system will be upgraded to detect the Hazardous chemicals from safe distance up to hundreds of meters The design of DAEDS is highly sophisticated sensitive and compact The mechanism and need of customized DAEDS is illustrated in the following paragraphs LABVIEW is being utilized for the control of the equipments and processing of the incoming signal Through LABVIEW all types of instrumentation equipments can be virtually configured without the need of actual hardware through a single screen GUI and via a single user Corresponding author Ramesh C Sharma Laser Science amp Technolgy Centre DRDO Delhi 110054 India Tel 04024347630 E mail rameshsharma las
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