What is CO2 CARS by yxc91345

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									          Infrared CARS:
   A Novel Sensor for Chemical,
 Biological and Nuclear Detection

                             Poster ID: 1412

                         Roger K. Richards
                    Oak Ridge National Laboratory


                                April 27, 2005

OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                    1
            Infrared Coherent Anti-Stokes
                  Raman Scattering
                   (Infrared CARS)
     • Chemical sensor
     • Uses a nonlinear interaction of two infrared
       lasers and the energy levels of a molecule
     • Remote sensing capabilities
     • Fast response
     • Ultra sensitive


OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                      2
                             Why Infrared?

   • Close to the desired wavelength for
     examining complex chemicals
   • Good atmospheric transmission
   • High power/efficient sources available
   • Background of infrared laser development
     at ORNL
   • Ultra-sensitive detection available

OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                3
        What is the scattering process?

  Virtual States
                                                   ω3 = 2ω1 - ω2



                                     ω1
                             ω2                            ω3
             ω1

                                          ωres = ω1 - ω2

OAK RIDGE NATIONAL LABORATORY
                                  Molecular Energy States
U. S. DEPARTMENT OF ENERGY
                                                                   4
               SOME BEAM GEOMETRIES




OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                      5
                  ABSORPTION SPECTRA




                                  Strong unique
                                chemical signatures
                                  for the different
                                    explosives




OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                  6
    TERAHERTZ TRANSMISSION IS POOR
  INFRARED TRANSMISSION CAN BE GOOD

                             Terahertz = 1012 Hertz




                                         Thz




OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                      7
  ORNL developed a CO2 laser-based Thomson scattering
  diagnostic for the US fusion program. Tests on this diagnostic
  were performed at ORNL, MIT, and as part of an international
  collaboration, in Japan.

Photo of CO2 laser-
based Thomson
scattering diagnostic
showing a 20J pulsed
laser under
construction




OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                               8
     ORNL Prototype Compact, Portable,
               CW CO2 laser

     • 2.4-mm dia x 20-
       cm discharge
     • Nominal 1-watt
       IR power
     • Air-cooled
     • Sealed system
     • 35-watts RF
       drive


OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                     9
 Infrared CARS Proof-of-Principle Test

                                   Successfully
                                Distinguished D2O
                                     From H2O




OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                               10
  PROOF-OF-PRINCIPLE TEST LAYOUT
              INFRARED LASER #1
                                                                        ,k 2
                                  BE
                                    AM                             ω   2
                                         #1
                                              TEST CELL



                                     M
                                         #2                        ω
              INFRARED LASER #2   BEA                                  1 ,k
                                                                           1




                                                  k 3= ω 1- ω
                                                    ω3

                                                      2k 1
                                                       =2

                                                          -k 2
                                                               2
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                                               11
     Experimental Results Show Signal
          From Deuterated Water
                                     (First DATA)

                        0.015



                                                             LASER
                        0.010                                D20
               SIGNAL




                        0.005



                            0



                        -0.005
                                 0     0.5             1.0           1.5

                                         TIME (MICROSEC)
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                                           12
              Remote Sensing Capability
                 (Fixed Checkpoint)
                                Sensor
                  Las                         Reflector
                      er #
                          2




                 Laser #1




                        or
                  Detect
                                Measurement
                                  Volume
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                          13
              Remote Sensing Capability
                   (On the Road)   Reflector
                                         (car, rock,
                                System   building, etc)


                 Laser #1,2




                                         Signal
                        or
                  Detect



OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                          14
                Problems to Consider with
                     Remote Sensing
   • Access to third beam (scatter off background
     structure vs direct detection)
   • Range – size of transmitting/collecting optics
   • Beam power – energy requirements/air
     breakdown
   • Interference from window materials



OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                      15
                    Footprint for Infrared CARS
                         in HVAC System
                      (Semi-Remote Sensing)



                       Source            Detector




OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                    16
    Wavelength Differences Accessible
            with CO2 Lasers
                                 DENSITY OF CO2 LASER LINE PAIRS

                         250


                         200
          NUMBER/10GHz




                         150


                         100


                         50


                          0
                          0.01         0.1              1          10

                                        FREQUENCY (THz)
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                                        17
                                Biosensor

     • Uses the high power lasers to breakdown
       biological specimens and then sample for
       unique chemical signature
     • Similar system already used to
       discriminate live from dead cells




OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                  18
                             Nuclear Sensor

     • Applicable for some nuclear detection as an isotope
       identification – e.g. tritium
     • Excellent background elimination
        − Signal is unique frequency
        − Signal is a directed beam
        − No radioactive decay considerations
     • Measurement is fast
     • Measurement is unique
        − Several resonances to compare in frequency
        − Compare amplitude ratios
     • Measurement is remote – no instrument contamination for
       subsequent measurements

OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
                                                                 19

								
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