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本文报告了一种用于γ射线照射量基准的石墨空腔电离室,采取球-圆柱形状,结构设计和材料选择保证了电离室良好的测量性能和稳定性。采用水称重法和几何尺寸测量相结合。精确测定了电离室体积。电离室内电场的合理分布,保证了可以得到良好的饱和特性。根据“等效壁厚”来考虑室壁的减弱效应,采用对“等效壁厚”外推的方法来得到室壁修正。用此电离室进行~(60)Co γ射线照射量测量的标准化,得到了满意的结果。测量照射量的合成不确定度为±0.25％。与BIPM的~(60)Co γ射线照射量测量比对,结果在0.16％以内一致,
In this paper, a graphite cavity ionization chamber for gamma irradiation is reported. The spherical-cylindrical shape, structural design and material selection ensure the good measurement performance and stability of the ionization chamber. Water weighing method combined with geometric dimension measurement. Accurate determination of the ionization chamber volume. The reasonable distribution of ionization indoor electric field ensures that good saturation characteristics can be obtained. According to the “equivalent wall thickness” to consider the attenuation effect of the wall, using the “equivalent wall thickness” extrapolation method to get the wall correction. The ionization chamber was used to standardize the measurement of ~ (60) Co γ-ray irradiation, and satisfactory results were obtained. The combined uncertainty of measured exposure is ± 0.25%. Compared with the measurement of ~ (60) Co γ-ray irradiation of BIPM, the results are consistent within 0.16%