Experimental results on enhanced water vapor measurement in vacuum chamber by Twin-TQCM utilizing an electric cooler instead of using liquid nitrogen

Japan Aerospace Exploration Agency, JAXA, and Nihon Dempa Kogyo Co., Ltd., NDK, developed an advanced Twin-QCM aiming for flight and exploration, which can be used under cryogenic temperature, i.e., lower than -80 degrees C called as “cryo-use Twin-TQCM (Engineering Model).” In the present study, the performance test results of the cryo-use Twin-TQCM in terms of measuring water vapor under vacuum is presented. As a result, stable deposition can be observed. Based on the results, the mass deposition rates were found to approximate in linear line, i.e., 127 ng/s at 30Pa and 120 ng/s at 3 Pa, respectively. From the measured data, the partial pressure of water can be calculated. When vacuum chamber was kept at 30 Pa of the total vacuum pressure, the partial pressure of water was 1.30 x 10^-2 Pa; at 3 Pa of the total vacuum pressure, the partial pressure of water was 1.23 x 10^-2 Pa, respectively. It just took 30 seconds to determine the partial pressure of water. It can be concluded that such measurement was achieved by the precise performance of the cryo-use Twin-TQCM.