Near%Infrared*Cavity*Ring%Down* Spectroscopy*System ......Measure*Other*Isotopes* Future*Plans* 6231...

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NearInfrared Cavity RingDown Spectroscopy System for CO 2 Isotope Detec<on Michael Finch, Adam Friss, Andrew Kustas, Jason Slavik Colorado State University, Department of Mechanical Engineering, Fort Collins, CO, 80526 1

Transcript of Near%Infrared*Cavity*Ring%Down* Spectroscopy*System ......Measure*Other*Isotopes* Future*Plans* 6231...

  • Near-‐Infrared  Cavity  Ring-‐Down  Spectroscopy  System  for  CO2  

    Isotope  Detec

  • Mo

  • CO2  Concentra

  • Cavity  Ring-‐Down  Spectroscopy  

    Laser Det.

    HR HR τo

    Laser Det.

    HR HR τ Absorber

    ( ) 01Absorbance R τ ττ

    ⎛ ⎞⎜ ⎟⎝ ⎠

    −= −

    0.0 0.2 0.4 0.6 0.8 1.00.0

    0.2

    0.4

    0.6

    0.8

    1.0

    Sig.

    [a.u

    .]

    Time [a.u.]

    0.0 0.2 0.4 0.6 0.8 1.00.0

    0.2

    0.4

    0.6

    0.8

    1.0

    Sig

    . [a.

    u.]

    Time [a.u.]

    4  

  • Experimental  Setup  /Components  

    Laser  

    Op

  • System  Schema

  • Laser  and  Collima

  • Acousto-‐Op

  • Op

  • Primary  Detector  

    •  Parabolic  focusing  mirror  •  Indium  gallium  arsenide  diode  •  Adjustable  gain  selngs  

    Parabolic  Mirror  

    10  

  • Secondary  Detector/Etalon  

    •  Rela

  • Data  Acquisi

  • Ring-‐Down  Times  •  Laser  temperature  is  set  

    and  current  is  scanned  via  triangle  wave    

    •  Upon  experiencing  resonance,  the  AOM  is  triggered  off  for  approx.  2  milliseconds,  at  which  point  laser  light  is  no  longer  entering  the  sampling  cell  

    •  During  this  

  • Data  Processing  

    •  Ring-‐down  

  • Data  Processing  •  Aper  recording  mul

  • Data  Processing  

    •  The  area  underneath  the  fit  is  then  found  using  numerical  integra

  • Results  

    Pressure  (atm)   Ave.  Conc.  (ppm)   %  error  0.05   397   1.8  0.15   382   1.9  

    Pressure:  0.05  atm  Sample   Conc.  (ppm)  

    1   398.3  2   399.3  3   396.2  4   396.2  5   396.7  

    St.  Devia

  • Future  Plans  

    Currently,  the  system  is  limited  in  terms  of  accuracy.    A  reliable  spectroscopic  device  must  have  very  high  accuracy.    As  such,  one  of  the  primary  goals  in  the  future  is  to  improve  the  accuracy  of  this  bench-‐top  CRDS  system.    In  general,  several  approaches  can  be  considered  to  improve  accuracy:    •  Using  a  calibra

  • Addi

  • Another  goal  of  the  system  is  to  measure  concentra

  • Inves

  • Lessons  Learned  

    •  Projects  ALWAYS  take  much  longer  than  expected  •  Do  not  plan  for  a  budget  that  has  not  yet  been  received  

    •  Alignment  of  op

  • •  htp://en.wikipedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide-‐en.svg  •  htp://www.tecnozono.com/CO2-‐dioxido-‐de-‐carbono.htm  •  htp://en.wikipedia.org/wiki/File:Beer_lambert.png  •  htp://decadal.gsfc.nasa.gov/ascends.html  •  htp://www.industrysearch.com.au/products/images/84530.jpg  •  htp://www.ni.com/images/coreblock/large/lvlogo_vert.gif  

    References  

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