23 June, 4:58 OSU-2009 TG13 1 Real time in flight detection of methane, nitrous oxide, carbon dioxide and nitric oxide using a chirped QC laser spectrometer Kenneth G. Hay Geoffrey Duxbury and Nigel Langford, a Department of Physics University of Strathclyde Glasgow, Scotland

23 June, 4:58 OSU-2009 TG13 2 Outline of Talk Resolution of intrapulse QC laser spectrometers Development of a single channel QC laser spectrometer for airborne trace gas measurements Extensions of airborne measurements using a compact four laser spectrometer. Future developments

23 June, 4:58 OSU-2009 TG13 3 The 3 band of CF 3 CH 3. A comparison of QC spectrum and that of an FTS, resolution cm -1. broad feature is a hot band Q branch

23 June, 4:58 OSU-2009 TG13 4 The 3 band of CF 3 CH 3. Expanded section with slow chirp, ca 20 MHz/ns,of QC laser. Note similarity of resolution, slight rapid passage shape of QC spectra

23 June, 4:58 OSU-2009 TG13 5 Installation of the QC spectrometer in the NERC ARSF Aircraft Setting up in the Dornier Vacuum system Forward facing inlet

23 June, 4:58 OSU-2009 TG13 6 Samples of in flight spectra Rep. rate 20 kHz, 20,000 averages per second. (a) takeoff from Oxford Airport, n nitrous oxide, m, methane. (b) descending to Haverfordwest Airport, (c) comparison of the intensity of the water absorption line, w2, at mid flight, (black), and on landing at Haverfordwest, (grey).

23 June, 4:58 OSU-2009 TG13 7 Flight path from Oxford to Haverfordwest (grey), return flight (black), derived from the GPS map. Flight altitude, and pressure variation within the absorption cell outback

23 June, 4:58 OSU-2009 TG13 8 Methane and nitrous oxide concentrations measured on the flights between Oxford and Haverfordwest airports. (a) outbound flight, (b) return flight. K.G. Hay, S.Wright, G. Duxbury, N. Langford Applied Physics B90, (2008) DOI /S x

23 June, 4:58 OSU-2009 TG13 9 Four laser intra-pulse spectrometer Inside view of Cascade Technologies four laser spectrometer Additional cooling System in lowest Section installed Post flight.

23 June, 4:58 OSU-2009 TG13 10 Control laptop and laser box in ARSF plane February 2009 Real-time concentration output Four laser box on RHS, ethernet connection to laptop

23 June, 4:58 OSU-2009 TG13 11 Expanded concentration output Top CO 2 Next N 2 O Third NO Bottom NO 2 (zero detection )

23 June, 4:58 OSU-2009 TG13 12 N 2 O laser, 500 averages m, methane; n, nitrous oxide Pixel number (1 pixel per ns ).

23 June, 4:58 OSU-2009 TG13 13 N 2 O laser, transmission m, methane; n, nitrous oxide 500 averages per spectrum

23 June, 4:58 OSU-2009 TG13 14 CO 2 laser, transmission Overlapped raw spectra, single Visible absorption line is due to CO. 500 averages per spectrum

23 June, 4:58 OSU-2009 TG13 15 CO 2 laser, transmission (a) and (b) Spectrum 488 used as transmission baseline. Transmission spectra (c), black as (a) and (b), red, uses interpolated background. Difference shows the drop in CO2 following startup of plane. 500 averages per spectrum

23 June, 4:58 OSU-2009 TG13 16 Conclusions Spectrometers based upon the intrapulse method are very useful for gas sensing They can operate in vibrationally noisy environments They have high sensitivity and good (for rapid measurement systems) frequency coverage This can be exploited for large scale monitoring projects. Sensors based on the intra-pulse method has been been developed by a Strathclyde University spinout, Cascade Technologies (CT), Stirling Science Part UK, for use in stack gas emissions, for example on large merchant ships. Marine Gases: SO x, NO x, CO, CO 2, H 2 O

23 June, 4:58 OSU-2009 TG13 17 Acknowledgements We are indebted to the the ERPSRC for an instrumentation grant and to NERC for the award of a COSMAS grant. GD is grateful to the Leverhulme Trust for the award of an Emeritus Fellowship, We would also like to thank Ruth Linley of Cascade Technologies for her support in the deployment of the prototype four QC laser spectrometer.