Simulation of the Wall Correction Factors and Physical Constants of 250~600 kV X-ray Graphite Cavity Ionization Chamber
WANG Bo1,2,WU Jin-jie2,DU Hai-yan3,REN Shi-wei1
1. Hebei University of Science and Technology, Shijiazhuang, Hebei 050000, China
2. National Institute of Metrology, Beijing 100029, China
3. Shanghai Jiao Tong University, Shanghai 200240, China
Abstract：Graphite cavity ionization chamber due to higher energy has good energy response, is widely used in 137Cs(effective energy of 662keV), 60Co (effective energy of 1250keV) and average energy is 350keV 192Ir gamma ray air kerma.The EGSnrc program was used to simulate the wall correction factor and physical constant of the self-made graphite cavity ionization chamber in the process of quantitative reconstruction under 250~400kV narrow spectrum radiative mass. The results showed that there was a significant relationship between the blocking power ratio of graphite and air, the mass energy absorption coefficient of air and graphite, and the proportion constant of toughened radiation, and the average energy. With the increase of X-ray energy, the wall correction factor had a tendency of first increasing and then decreasing, and it could not determine the future trend. The results of monte carlo simulation provide technical data for establishing 250~600kV X-ray air kerma national benchmark and realizing the reappearance of measurement values, and meet the expected requirements of the uncertainty of measurement of the reappearance results.
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2018, Vol. 39 
