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Water vapour spectroscopy in the MSF Dr Robert McPheat CAVIAR Progress Meeting NPL 02/06/2008.

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Presentation on theme: "Water vapour spectroscopy in the MSF Dr Robert McPheat CAVIAR Progress Meeting NPL 02/06/2008."— Presentation transcript:

1 Water vapour spectroscopy in the MSF Dr Robert McPheat CAVIAR Progress Meeting NPL 02/06/2008

2 SPAC Short path-length absorption cell (SPAC) –1.2 to 20 metres –Multi-pass reflective optics (White) –Being upgraded for CAVIAR -200 to 200ºC temperature range 5 bar maximum pressure No cold spots (including valves, feedthroughs etc.) Mirrors adjustable from outside Accurate temperature & humidity measurement Corrosion resistant Made first measurements Problems with thermal expansion –Can be used for hot measurements

3 SPAC upgrade OpticsInnerCooling Jacket

4 High temperature pressure gauge & filling line Temperature & pressure logging Temperature control Outer vacuum jacket Transfer optics vacuum tank Detector box

5 SPAC upgrade modifications

6 Second High Resolution Spectrometer Bruker IFS120 HR Upgrade –Upgraded electronics / moving mirror to same specification as IFS125 –Maximum spectral resolution of 0.0015 cm -1 –Spectral range of 10 to 40,000 cm -1

7 LPAC Vacuum Upgrades Replace unreliable pumps & gauges (dating from early 1970s) Oil free to avoid contamination –3 large dry pumps –1 dry backing pump –6 new gauges

8 Future Work Measurement of unsaturated strong lines Finish SPAC modifications –Measurements covering visible to FIR Need window & detector box modifications for FIR –Up to 450 K LPAC vacuum upgrade –Measurement conditions –243K to 293K –water pressures up to 0.75 SVP –resolution up to possible 0.0015cm -1 but mainly at 0.03cm -1 –water/air mixtures at total pressures of 150, 500 & 1000 hPa


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