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

SO3

(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

SO3

MEASUREMENT ADVANTAGES

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

Direct measurement actual optical resolution

SO3

MEASUREMENT ADVANTAGES

SO3

MEASUREMENT ADVANTAGES

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)

SO3

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

SO3

UNIQUE SAMPLING METHOD

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.

SO3

UNIQUE SAMPLING METHOD

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

SO3

DIRECT SO3 MEASUREMENT

SO3

H2O

SO3

H2O effects selectively removed

PUTTING IT ALL TOGETHER

SO3

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

SO3

Direct SO3 measurement with the

ProCEAS Cavity Enhanced

Spectrometer