球形不锈钢电离室响应实验研究

EXPERIMENTAL STUDY ON RESPONSE OF THE STAINLESS STEEL BALL-SHAPED IONIZATION CHAMBER

针对球形不锈钢电离室,开展了一系列实验研究,包括不同充气气体及其不同气压条件下的电离室的能量响应及单位压力灵敏度等。实验气体包括氦气、氮气、氩气、氪气和氙气,原子序数从2到54;充气气压从4 kPa到1 000 kPa;照射射线能量从33 keV到1.25 MeV。研究结果表明:1)对不锈钢电离室,在充氙气时最灵敏,在相同充气压力下,对137Cs源和低能射线(83 keV)照射,充氙电离室的灵敏度约分别为充氩电离室的5.6倍和55倍;但在实验中发现,对充氙气电离室的灵敏度随压力变化曲线,当射线能量超过205 keV时,在计示0.2个大气压处存在拐点,还有待进一步分析。2)从能量响应来看,充氩的最好,充氙的最差,充氦和氮的居中且两者大致相同。

A series of experiments for the stainless steel ball-shaped ionization chamber have been performed, including the energy responsing of the chamber and the sensitivity per unit pressure of the chamber for different gases filled under different gas pressures. In experiments, the gases include He, N2, Ar, Kr and Xe with atomic numbers from 2 to 54, the gas pressures in the chamber are from 4 kPa up to 1000 kPa, and the energies of exposure rays from 33 keV to 1.25 MeV. The results show that, 1 ） the Xe-filled chamber is the most sensitive, and its sensitivity is 5.6 times that of the Ar-filled chamber under the exposure of 137^Cs and the same pressure; the Xe-filled chamber is more sensitive than the Ar-filled one （the difference of the sensitivity is 55 times） under the exposure of the ray with low energy （83 keV）. It was found in the experiments that the sensitivity curve with pressure of the Xe-filled ionization chamber has an inflexion at 0.2 atm, when exposure energy is in excess of 205 keV. This phenomena remain to be further analyzed. 2） for the energy response of ionization chamber, the Ar-filled ionization chamber is the best, the Xe-filled ionization chamber the worst, the energy response of Ar-filled chamber is similar to N2-filled chamber.