基于~(90)Sr源β射线的外推电离室入射窗修正因子
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摘要
为实现外推电离室对β辐射吸收剂量的准确测量,对影响外推电离室入射窗修正因子k_(wi)的主要量进行了研究。实验测量了外推电离室不同极间距和不同源-探距(源到外推电离室入射窗表面的距离)下的k_(wi)。研究结果表明,在源-探距不变的条件下,k_(wi)随电离室极间距的增大而减小;在电离室极间距为3 mm的条件下,k_(wi)随源-探距的增大而减小。利用蒙特卡罗模拟计算出不带展平过滤器、源-探距为30 cm、电离室极间距为3 mm时,k_(wi)为1.084 5,与实验测量结果比较,其相对偏差为0.11%。因此,在给出k_(wi)的同时,应提供相应的源-探距和电离室极间距。
In order to achieve accurate measurement of the absorbed dose of beta radiation, the main influence factors of the extrapolation chamber entrance window correction factor k_(wi) were studied. k_(wi) at different cavity lengths and different source-detection distances was measured by experiments. The results show that the correction factor k_(wi) with the same source-detection distance decreases with the increase of the cavity length. And k_(wi) decreases with the increase of the source-detection distance when the cavity length is 3 mm. The calculated k_(wi) without flattened filter at source-detection distance of 30 cm and cavity length of 3 mm was simulated using Monte Carlo method. The simulation result is 1.084 5, which differs from the experiment result by 0.11%. Therefore, in addition to the correction factor k_(wi), corresponding source-detection distance and cavity length should be supplied.
In order to achieve accurate measurement of the absorbed dose of beta radiation, the main influence factors of the extrapolation chamber entrance window correction factor k_(wi) were studied. k_(wi) at different cavity lengths and different source-detection distances was measured by experiments. The results show that the correction factor k_(wi) with the same source-detection distance decreases with the increase of the cavity length. And k_(wi) decreases with the increase of the source-detection distance when the cavity length is 3 mm. The calculated k_(wi) without flattened filter at source-detection distance of 30 cm and cavity length of 3 mm was simulated using Monte Carlo method. The simulation result is 1.084 5, which differs from the experiment result by 0.11%. Therefore, in addition to the correction factor k_(wi), corresponding source-detection distance and cavity length should be supplied.
引文
[1] HELMST?DTER K,B?HM J,AMBROSI P,et al.Supplementary comparison:Comparison of extrapolation chamber measurements of the absorbed dose rate for beta radiation between VNIIM (Russia) and PTB (Germany)[J].Metrologia,2004,41(1A):06008.
[2] LECANTE C,URYAEV I,VILLEVALDE N,et al.Supplementary comparison:Comparison of extrapolation chamber measurements of the absorbed dose rate in beta radiation[J].Metrologia,2004,41(1A):06009.
[3] BEHRENS R,FEDINA S,OBORIN A.Direct comparison of extrapolation chamber measurements of the absorbed dose rate for beta radiation between PTB (Germany) and VNIIM (Russia)[J].Metrologia,2011,48(5):317-323.
[4] BEHRENS R,HELMST?DTER K,AMBROSI P,et al.International comparison EUROMET.RI(Ⅰ)-S2 of extrapolation chamber measurements of the absorbed dose rate in tissue for beta radiation (EUROMET project No 739):Final report[J].Metrologia,2007,44:06003.
[5] ISO 6980-2 Reference beta-particle radiation,Part 2:Calibration fundamentals related to basic quantities characterizing the radiation field[S].[S.l.]:[s.n.],2004.
[6] SKUBACZ K.Application of the B?hm chamber for reference beta dose measurements and the calibration of personal dosimeters[J].Nukleonika,2016,61(1):61-67.
[7] 万兆勇,李延波.β吸收剂量绝对测量装置[M]//中国核科技报告.北京:中国原子能出版社,1998.
[8] BAKSHI A K,VANDANA S,SELVAM T P,et al.Measurement of the output of ISO recommended beta sources with anextrapolation chamber[J].Radiation Measurements,2013,53-54(5):50-55.
[9] B?HM J.The national primary standard of the PTB for realizing the unit of the absorbed dose rate to tissue for beta radiation,PTB Report DOS-13[R].[S.l.]:[s.n.],1986.
[10] 邬蒙蒙,李德红,王培伟.圆柱型空腔电离室修正系数的Monte Carlo模拟与实验验证[J].计量学报,2016,37(2):214-218.WU Mengmeng,LI Dehong,WANG Peiwei.Monte Carlo simulation and experimental validation of correction factor for cylindrical cavity ionization chamber[J].Acta Metrologica Sinica,2016,37(2):214-218(in Chinese).
[11] BEHRENS R.Simulation of the radiation fields of the Beta Secondary Standard BSS 2[J].Journal of Instrumentation,2013,8(2):P02019.
[2] LECANTE C,URYAEV I,VILLEVALDE N,et al.Supplementary comparison:Comparison of extrapolation chamber measurements of the absorbed dose rate in beta radiation[J].Metrologia,2004,41(1A):06009.
[3] BEHRENS R,FEDINA S,OBORIN A.Direct comparison of extrapolation chamber measurements of the absorbed dose rate for beta radiation between PTB (Germany) and VNIIM (Russia)[J].Metrologia,2011,48(5):317-323.
[4] BEHRENS R,HELMST?DTER K,AMBROSI P,et al.International comparison EUROMET.RI(Ⅰ)-S2 of extrapolation chamber measurements of the absorbed dose rate in tissue for beta radiation (EUROMET project No 739):Final report[J].Metrologia,2007,44:06003.
[5] ISO 6980-2 Reference beta-particle radiation,Part 2:Calibration fundamentals related to basic quantities characterizing the radiation field[S].[S.l.]:[s.n.],2004.
[6] SKUBACZ K.Application of the B?hm chamber for reference beta dose measurements and the calibration of personal dosimeters[J].Nukleonika,2016,61(1):61-67.
[7] 万兆勇,李延波.β吸收剂量绝对测量装置[M]//中国核科技报告.北京:中国原子能出版社,1998.
[8] BAKSHI A K,VANDANA S,SELVAM T P,et al.Measurement of the output of ISO recommended beta sources with anextrapolation chamber[J].Radiation Measurements,2013,53-54(5):50-55.
[9] B?HM J.The national primary standard of the PTB for realizing the unit of the absorbed dose rate to tissue for beta radiation,PTB Report DOS-13[R].[S.l.]:[s.n.],1986.
[10] 邬蒙蒙,李德红,王培伟.圆柱型空腔电离室修正系数的Monte Carlo模拟与实验验证[J].计量学报,2016,37(2):214-218.WU Mengmeng,LI Dehong,WANG Peiwei.Monte Carlo simulation and experimental validation of correction factor for cylindrical cavity ionization chamber[J].Acta Metrologica Sinica,2016,37(2):214-218(in Chinese).
[11] BEHRENS R.Simulation of the radiation fields of the Beta Secondary Standard BSS 2[J].Journal of Instrumentation,2013,8(2):P02019.