Development of 2.2 μm cavity ring-down spectrometer for tritiated water analysis

Abstract

A rapid and simple tritium analysis method is required for tracer application and quantitative evaluation of radioactive waste. In this study, we focused on cavity ring-down spectroscopy, which is an ultra-sensitive laser absorption spectroscopy, and developed a spectrometer for tritium analysis. A current modulation-assisted acoustic optical modulator switching method was developed in the prototype setup containing a 2.2 μm diode laser for accessing the 2ν1 absorption band of HTO water vapor. The benefit of this switching method was investigated using the Allan deviation and compared to conventional acoustic optical modulator-only and current-only switching methods. Using the prototype setup with the proposed switching method, cavity ring-down spectroscopy of stable H2O vapor was demonstrated. The detection limit for liquid tritium water analysis was estimated to be 2× 101 kBq/10 µL for ten minutes measurement.