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