1. Department of Radiation Oncology, North China University of Science and Technology Affiliated Hospital,Tangshan, Hebei 063000, China
2. National Institute of Metrology, Beijing 100029, China
3. School of Science, Hebei University of Science and Technology, Shijiazhuang,Hebei 050018, China
Abstract：To complete the absolute measurement of the reference air kerma rate of the high dose rate 192Ir radioactive source, a special irradiator and positioning device was designed, and a collimated reference radiation field was built using a medical high dose rate brachytherapy machine. Concerning relevant standards such as ISO 4037, the scattering, radiation field, half-value layer, effective energy and other related parameters of the reference radiation field were measured. The results show that the ambient scattering share is less than 0.003% of the main beam at multiple locations in the radiation field; at a distance of 1.4 m from the radiation source, the diameter of the radiation field is 98 mm, which is larger than the benchmark graphite cavity ionization chamber; the layer measurement result is Cu of 8.224mm,and the effective energy is 402.8keV. The 192Ir energy spectrum measured by HPGe detector is in good agreement with the simulated spectrum. All the parameters met the requirement of the 192Ir brachytherapy source reference air kerma rate to reproduce the magnitude, which laid the foundation for its absolute measurement and international comparison.
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2023, Vol. 44 
