| 摘要 |
PURPOSE: To heighten the effective signal/background noise ratio so as to improve the measurement efficiency by coating the inner wall of an aluminium enclosure with a lead layer, and charging the enclosure with argon gas. CONSTITUTION: The inner surface 2 of an enclosure 1 formed of aluminium is coated with a lead layer 0.5-1mm thick which can absorb photons of 100KeV or less, and the enclosure is charged with argon gas with 5-10 bar. A cylindrical center electrode 4 and a high voltage electrode 3 are concentrically disposed, and respectively supported by supports 5, 6 made by insulating coating conductive material to be connected to a power supply through connecting wires 7, 9. A threaded base 15 of the enclosure 1 is fixed to a hot branch of a pressurized watwe reactor, for example. When voltage is applied to the electrodes 4, 3, a continuous potential difference is produced between the electrodes to establish an electric field in a gas volume. Accordingly, a gamma-ray entering across a detector causes argon to be ionized to emit charges, and the charges are collected by the electrodes 4, 3.
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