Purity measurement of liquid methane by using the drift property of ionized electrons

The purity is important parameter for the collection of electrons ionized in an ionization chamber filled with the liquid methane. The methane gas purification system was developed for the liquid methane ionization chamber. After the condensation of the purified methane gas in the ionization chamber mounted with 241 Am alpha source, ionized electrons were collected by a charge sensitive preamplifier. The concentration of impurity of oxygen gas was obtained by analyzing a collected charge distribution. Pulse height distributions of a charge sensitive preamplifier were obtained for the detection of y rays and neutrons emitted from 60Co, 137Cs and Am-Be sources located outside the cryostat of the liquid methane chamber.