Abstract

A rapid and simple tritium analysis method is required for tracer application and the quantitative evaluation of radioactive waste. In this study, we focused on cavity ring-down spectroscopy (CRDS), 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 tritiated 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, CRDS 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-minute measurements.