Optical Feedback Cavity Enhanced Spectroscopy

AP2E

FRANCE

Direct SO3 measurement with the

ProCEAS Cavity Enhanced Spectrometer

SO3

OFCEAS

(Hyper-reflective gas cell mirrors reflectivity`99.999%)

MEASUREMENT ADVANTAGES

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(Same energy emission becomes concentrated in narrower band- Governed by Lavoisier’s Law of Energy Conservation)

No FeedbackBandwidth 1 MHzIntensity 1X

FeedbackBandwidth 10 kHzIntensity 10X

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200 pt high resolution spectrum(1500 nm source used as example)

Direct measurement actual optical resolution

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Actual 11 day accuracy and drift tests results comparing w/ GC for sample gas CH4 shown

Results show 20ppb or 1% drift over 11 days compared w/ reference GC recalibrated every 30 mins

(References: Romanani et al. report to Atmospheric Stations Instrumentation Workshop 2008; Chappellaz report at NEEM Gas Consortium Meeting Copenhagen 2009)

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UNIQUE SAMPLING METHOD

Reduced pressure sampling probe w/ sonic velocity nozzle

Supports accelerated sample transport times; typical – 5 seconds for every 3 meters (@ 0.2 scfm flow rate)

Low flow (typically 0.11-0.33 scfh) allows for low cost precision vacuum pump. Sample line only ~ 4mm ID

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100 meter sample line on post combustion SCR outlet has been demonstrated with conditions of sample pt. temp ~200 deg C, 15% H2O by Vol and using UNHEATED line

Thermodynamic sampling conditions at the actual sampling point are effectively moved to more advantageous conditions for sampling.

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The diagram shows how absorption peak selectivity can clearly be manipulated with sample line vacuum pressure

Diagram reference: as reported by authors Lonigro & Lanher at IFPAC 2010 Baltimore

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DIRECT SO3 MEASUREMENT

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H2O

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H2O effects selectively removed

PUTTING IT ALL TOGETHER

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TDLAS – Tunable Diode Laser Absorption Spectroscopy; CRDS – Cavity Ring Down Spectroscopy

SO3

Direct SO3 measurement with the

ProCEAS Cavity Enhanced

Spectrometer

Optical Feedback Cavity Enhanced Spectroscopy

Engineering