Note: Reliable, robust measurement system for trace moisture in gas at parts-per-trillion levels using cavity
Hisashi Abe1, Daniel Lisak2, Agata Cygan2
1National Metrology Institute of Japan (NMIJ), AIST, Tsukuba Central 3, Tsukuba 305-8563, Japan.
Abstract:
We report a simple, robust cavity ring-down spectroscopy system to reliably measure trace moisture in gases at parts-per-trillion (ppt) levels. The performance of the system was evaluated on the basis of experiments performed in a manner traceable to the International System of Units. The obtained result was in good agreement with the primary trace-moisture standard at 12 nmol/mol (12 ppb) in N2 in amount-of-substance fraction. Measurement capability of residual moisture in high-purity dry N2 at ∼130 pmol/mol (130 ppt) was demonstrated, and background noise of 5.3 × 10(-12) cm(-1) was attained, corresponding to a minimum detectable H2O of 5 pmol/mol (5 ppt).
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