基于正比计数器的低能X射线空气比释动能测量研究

Study on the Measurement of Low Energy X-ray Air Kerma Based on Proportional Counter

为准确测量低能低剂量率X射线,依托10~60 kV X射线光机,在低空气比释动能系列辐射质基础上,通过继续添加附加过滤的方式,建立了7个参考辐射质。运用蒙特卡罗模拟程序得到各辐射质的能谱,并计算其半值层和平均能量。采用正比计数器完成能谱的测量,模拟能谱与实测能谱的平均能量相对偏差不超过6%。利用PTW34047电离室通过逐级替代法完成空气比释动能率的测量,对正比计数器进行校准测量,得到能谱-剂量转换函数。最后对能谱-剂量转换函数进行验证,与电离室法得到的结果偏差不超过3.8%;采用AT1123巡测仪验证,其相对偏差在9%以内。

The monitoring and protection of low energy X-ray was increasingly important.For crystal detectors,such as CZT and NaI detectors,it is of great significance to study the energy response in the low energy range for the development and application of instruments.In order to accurately measure low-energy and low-dose-rate X-ray,based on 10~60 kV X-ray machine,seven reference radiation quality were established by adding additional filtration on the basis of low air kerma series radiation quality.The energy spectrum of radiation quality by Monte Carlo simulation program were obtained,and half-value layer and average energy were calculated.The proportional counter was used to complete the measurement of the energy spectrum.The results showed that the relative deviation between the simulated energy spectra and measured spectra does not exceed 6%.By used PTW34047 ionization chamber,the measurement of air kerma rate was completed by successive substitution method.The proportional counter was calibrated and the energy spectrum-dose conversion function was obtained.Finally,the energy spectrum-dose conversion function was verified,and the deviation from the results obtained by the ionization chamber method is not more than 3.8%.Verified by AT1123 survey meter,the relative deviation is within 9%.