H-450 X射线参考辐射质的研建及验证

根据PTB和ISO 4037-1:2019要求，关于高空气比释动能系列（H系列）X射线参考辐射质的推荐数据，外推得出H-450的附加过滤为6.24 mm Cu，第一半值层（HVL_1st）为(5.39~5.52)mm Cu，平均光子能量为(214.25~214.78)keV，剂量率为11.51 Gy/h（距离焦斑为1 m处，管电流为10 mA）。随后，使用PTW32005电离室作为测量器具，采用半值层法建立H-450 X射线参考辐射质，得出HVL_1st为5.37 mm Cu，第二半值层（HVL_2nd）为5.97 mm Cu，同质系数为0.9。最后，使用PTW30013次级标准电离室测量得出H-450 X射线参考辐射质下距离焦斑1 m，管电流为10 mA时的剂量率值为11.98 Gy/h，与理论值的相对误差为4.07 %。采用MCNP 5软件对H-450 X射线参考辐射质进行能谱模拟并计算得出其平均光子能量为200.4 keV。

Establishment and Verification of H-450 X-ray Reference Radiation Quality

Based on the recommended data from PTB and ISO 4037-1:2019 on the high air kerma series (H series) X-ray reference radiation quality,it is extrapolated that the additional filtration of H-450 is 6.24 mm Cu,the first half value layer (HVL_1st) is (5.39~5.52) mm,the average photon energy is (214.25~214.78) keV,and the dose rate is 11.51 Gy/h (the distance between the focal spot and the point test is 1 m,the tube current is 10 mA).Subsequently,the H-450 X-ray reference radiation quality was established by the half-value layer method and the PTW32005 ionization chamber as the measuring instrument.It is obtained that HVL_1st is 5.37 mm Cu,the second half value layer (HVL_2nd) is 5.97 mm Cu,and the homogeneity coefficient is 0.9.Finally,the dose rate of H-450 X-ray reference radiation measured by PTW30013 secondary standard ionization chamber is 1.198 Gy/h,on condition that the distance between the focal spot and the point test is 1 m and the tube current is 10 mA,and the relative error with the theoretical value is 4.07 %.The energy spectrum of H-450 X-ray reference radiation is simulated by MCNP5 software,and the average photon energy is calculated as 200.4 keV.