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Progress in water vapour spectroscopy at RAL
Dr Robert McPheatCAVIAR Progress Meeting
NPL, 29/09/2010
Plan for mid-IR measurements
800 – 2100 cm-1, 12.5 – 4.8 µm
Saturated PH2O (mb) !
T (K) P (mb) P (mb)
13.8 285 ? 10F
19.1 290 10, 15F 27.8 296 20(F) 10, 15F, 20
62 310 50 20(F)
No Argon steps are needed for LPAC measurements
135 325 100 20(F)
270 340 100, 150, 200
510 355 100, 150, 200, 350
Resolution (cm-1):
N of scans:
0.01 0.02 | 0.05
0.003
? (to ensure good S/N)
| SPAC, 20m | LPAC, 512m
(F) Only foreign measurement: H2O + Air(1.5atm) F Foreign measurement: H2O + Air(1.5atm), in addition to the pure one
LPAC measurements
512 m path length, 31 imagesHigh accuracy Baratrons & PRTsRoom kept at 297 KInitial problems stable WV pressure
LPAC Window problems
LPAC Measurements
New water vapour injection system
Sample
Gauge
Air
LPAC S/N Measurements
700 – 2100 cm-1 0.003 cm-1 resolution Set aperture for 1300 cm-1 LWP filter 1300 cm-1 0.006 cm-1 resolution