Performance Experiments of the Humidity Control System in the ²²⁰Rn Chamber

Abstract

This paper describes performance experiments of a humidity control system in a thoron ²²⁰Rn chamber which adjusts and controls the humidity inside the chamber. The easily constructed and used humidity control system has a perfluorosulfonic membrane (commercially known as Nafion^®) tube as the air humidity conditioner. The tube includes tube moisture exchangers that allow the transfer of water vapor between a flowing sample gas stream and a flowing purge gas stream over the exterior surface of the tube. Thus the tube has an advantage of being able to adjust the sample air flow to the desired humidity conditions. We investigated the optimal operation of the air humidity conditioner, including such items as response time to humidity, ability to control the humidity in the air and the losses of ²²⁰Rn gas in passing through the air humidity conditioner. Our first experiment showed that the performance of the air humidity conditioner depended on the flow rate conditions of sample and purge air flows. Only small losses due to decay of ²²⁰Rn and adsorption of ²²⁰Rn gas onto the tube surfaces were also evident. In the second experiment with the ²²⁰Rn chamber, we were able to adjust and control the humidity in the chamber using the humidity control system with the air humidity conditioner.