near%infrared*cavity*ring%down* spectroscopy*system ......measure*other*isotopes* future*plans* 6231...
TRANSCRIPT
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Near-‐Infrared Cavity Ring-‐Down Spectroscopy System for CO2
Isotope Detec
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Mo
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CO2 Concentra
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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
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Experimental Setup /Components
Laser
Op
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System Schema
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Laser and Collima
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Acousto-‐Op
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Op
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Primary Detector
• Parabolic focusing mirror • Indium gallium arsenide diode • Adjustable gain selngs
Parabolic Mirror
10
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Secondary Detector/Etalon
• Rela
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Data Acquisi
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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
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Data Processing
• Ring-‐down
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Data Processing • Aper recording mul
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Data Processing
• The area underneath the fit is then found using numerical integra
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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
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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
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Addi
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Another goal of the system is to measure concentra
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Inves
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Lessons Learned
• Projects ALWAYS take much longer than expected • Do not plan for a budget that has not yet been received
• Alignment of op
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• 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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