Development of the dosimetry device with a magnetic levitation electrode ionization chamber which can measure a low level radioactive gas dose and neutron dose

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A purpose of this study is to develop a high sensitivity magnetic levitation electrode ionization chamber which can measure a low level radioactive gas dose and a low level neutron dose. The study period was 2008 years from 2006.At first, we developed a large-scale magnetically levitated electrode ionization chamber and examined a performance characteristic of the chamber with the volume of 8 liters. We confirmed that the ionization chamber can definitely measure low level radiation dose. We measured background dose under the condition that a device was put in an airtight container. We obtained the result that the opening of the chamber's shutter did not influence measurement of background. We measured also dose rate of background by the ionization chamber with the different volumes of 1, 8 and 14 liters simultaneously. Then, we obtained the same experimental results about magnitude and time fluctuation of the dose equivalent rate; even if ionization volumes were different. In measurement of 8 liters ionization chamber under time intervals 10, 30 and 60 minutes, a detection limit with reliability, 68% were 0.0054, 0.0027 and 0.0012 μSv/h, respectively.At the next stage, we developed a differential type dosimetry device used a magnetic levitated electrode ionization chamber. This device is able to measure the space charge of 10-16A level. With this device, we measured very feeble tritium gas. Furthermore, by improving this device, we measured doses of a thermal neutron.We announced these findings to Meeting of Atomic Energy Society of Japan. In addition, our articles was published by the RADIOISOTOPES(Vol.55, No.7) and the IEEE Transaction on Nuclear Science(Vol.53,No.4).