一种用于Hp(3)测量的电离室性能评价

人眼晶体易受辐照损伤，为直接测量人眼晶体的个人剂量当量Hp(3)，通过自研的一种人体头颅模型，在眼球部位嵌入球形电离室，开展辐射环境中Hp(3)的准确性评价。首先在GB/T 12162.1标准中规定的S-Cs辐射质条件下对该仪器进行校准，再利用该校准因子在不同能量和入射角条件下测量，获得相应的能量和入射角修正因子k(E,α)，同时对其本底电流和极化效应进行测量，最后探讨该电离室测量值准确性的影响因素。结果表明，Hp(3)电离室的校准因子NH=1.19 μSv/pC；在未进行能量和入射角修正情况下，测得其在33 keV~1.25 MeV能量范围内响应相对误差为-0.9%~12.6%，-60°~60°入射角范围内的响应相对误差为-7.9%~0%。通过不确定度评定，得到其校准因子的相对扩展不确定度为5.6%（k=2）；能量和入射角已知、未知时，Hp(3)测量值的相对扩展不确定度分别为9.4%（k=2）和18%（k=2）。对于能量和入射角未知情况下的辐射场，在不确定度范围内可直接利用该电离室测量得到辐射场的Hp(3)。本研究可为眼晶体个人剂量当量的准确测量提供参考。

Performance Evaluation of an Ionization Chamber for Hp(3) Measurement

Human eye lens is an organ vulnerable to radiation damage. Through self-developed human skull model, a spherical ionization chamber was embedded in the ball to directly measure the eye lens individual dose equivalent Hp(3). Aiming at the accuracy evaluation of Hp(3) in radiation environment, the following research was carried out in this paper: Firstly, the instrument was calibrated under the S-Cs γ-ray radiation quality condition specified in the GB/T 12162.1 standard, and a calibration factor was obtained, NH=1.19 μSv/pC. Then, the correction factors k(E,α) were determined under different energy and incident angle conditions. At the same time, the background current and polarization effect were experimentally measured. Without the correction of energy and incident angle, the relative error of the energy response was -0.9%-12.6% in the energy range of 33 keV-1.25 MeV, and the relative error of the angle response was -7.9%-0% in the range of -60°-60°. At the same time, the factors affecting the accuracy of the measured value of the chamber were discussed. The relative expanded uncertainty of the calibration factor was 5.6% (k=2); when the energy and incident angle were known and unknown, the relative expanded uncertainty of the measured value of Hp(3) were 9.4% (k=2) and 18% (k=2) respectively. For radiation fields with unknown energy and incident angle, the Hp(3) value in the radiation field can be obtained directly by using the ionization chamber within the uncertainty range. This study can provide a reference for the accurate measurement of individual dose equivalent of eye lens.