An ionization chamber using a magnetically suspended electrode and its application to environmental radiation monitoring

A high-sensitivity ionization chamber has been developed for environmental radiation monitoring. The ion-collecting electrode is suspended by magnetic force without using all insulator so that the chamber is free from background current (such as leakage current and piezoelectricity) caused by the insulator. The electrode is reset periodically (every hour), and the ionization current is measured by detecting the amount of charge which flows through the reset contact. Experiments show that the chamber is useful for monitoring environmental gamma-ray dose (when the chamber is closed) or radon concentration in air (when the chamber is opened). The minimum detectable magnitude of ionization current is about 10/sup -17./ A, when the electrode is reset every hour.>