作者：杭仲斌^1,2, 田丽霞¹, 宋明哲², 王红玉², 刘川凤², 唐伟伟¹

作者单位：1. 东华理工大学，江西 南昌 330013;
2. 中国原子能科学研究院 计量校准与技术重点实验室，北京 102488

关键词：外推电离室;β射线;⁹⁰Sr/⁹⁰Y;⁸⁵Kr

摘要：

为实现外推电离室对β辐射吸收剂量的准确测量，按照外推电离室参数对性能的影响程度，对PTW23392型外推电离室进行漏电流、饱和曲线、离子收集效率、外推曲线和电离室零点位置与有效收集面积5大参数的测量。实验使用⁹⁰Sr/⁹⁰Y和⁸⁵Kr放射源（带展平过滤）进行测量和分析研究。极板间距取0.5 mm、1.0 mm、1.5 mm、2.0 mm、2.5 mm 5个位置，将极板间距外推至零，以求满足Bragg-Gray理论。实验得出结论：漏电流的范围为0.2~2.2 fA；由饱和曲线可知，当给外推电离室施加电压5 V、10 V、15 V、20 V、25 V时，外推电离室处于饱和区域；电离室离子收集效率均在99.3%以上；外推曲线的线性拟合度均在0.998以上。以上数据满足IEC-60731和IAEA TRS-398要求。通过电压阶跃法得出电离室的零点位置为0.0086 cm处，有效收集面积为7.2272 cm²。因此，可确定此外推电离室满足β辐射吸收剂量测量的基本要求。

Study of measurement method for key parameters of extrapolation chamber
HANG Zhongbin^1,2, TIAN Lixia¹, SONG Mingzhe², WANG Hongyu², LIU Chuanfeng², TANG Weiwei¹
1. East China University of Technology, Nanchang 330013, China;
2. National Key Laboratory for Metrology and Calibration Techniques, China Institue of Atomic Energy, Beijing 102488, China
Abstract: In order to realize the accurate measurement of radiation absorbed dose in the extrapolation chamber, the leakage current, saturation curve, ion collection efficiency, extrapolation curve and zero point position and effective collection area of the PTW23392 extrapolation chamber were measured according to the degree of influence of the parameters of the extrapolation chamber on the performance. The ⁹⁰Sr/⁹⁰Y and ⁸⁵Kr radioactive sources (with flattening filter) were used for measurement and analysis. The chamber depth was taken as 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm and 2.5 mm, and the chamber depth was extrapolated to zero, so as to meet the Bragg-Gray theory. The experiment concluded that the leakage current range was 0.2-2.2 fA. According to the saturation curve, when voltage 5 V, 10 V, 15 V, 20 V and 25 V are applied to the extrapolation chamber, the extrapolation chamber is in the saturation region. The ion collection efficiency of ionization chamber is above 99.3%. The linear fitting degree of the extrapolation curves was above 0.998. The above data all meet the requirements of the IEC-60731 and IAEA TRS-398. The voltage step method was adopted to obtain the zero point position of extrapolation chamber as 0.0086 cm and the effective collection area as 7.2272 cm².Therefore, it can be determined that the extrapolation chamber satisfies the basic requirements of radiation absorbed dose measurement.
Keywords: extrapolation chamber;β ray;⁹⁰Sr/⁹⁰Y;⁸⁵Kr
2021, 47(5):1-5,23  收稿日期: 2020-09-21;收到修改稿日期: 2020-11-03
基金项目: 国家自然科学基金项目（12075056）
作者简介: 杭仲斌(1993-),男,江苏南京市人,硕士研究生,专业方向为核科学与技术专业
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