Simulation calculation of wall correction factor of 192Ir gamma-ray spherical graphite cavity ionization chamber / 中华放射医学与防护杂志

ABSTRACT

Objective:To study the correction factor of the chamber wall of the reference air kerma rate reference ionization chamber (NIM-Ir-SG-100 type) for 192Ir radioactive source. Methods:The photon spectrum and ionization chamber wall correction factor of the radioactive source housing and irradiator model are calculated by Monte Carlo code. And then the photon energy, wall thickness and ionization chamber diameter, which affect the result of the chamber wall correction factor, are simulated.Results:After calculation, the simulation result of the correction factor of spherical graphite cavity ionization chamber wall was 1.037 7. Controlling a single variable, photon energy (0.3-1.3 MeV), wall thickness (0.2-0.5 cm), inner diameter (0.5 -15 cm), the maximum deviations of wall correction result were 1.62%, 3.30% and 2.86%, respectively.Conclusions:The self-made spherical graphite cavity ionization chamber has good performance, and the corrected kwall value of the chamber wall is within a reasonable range. The completion of the chamber wall correction factor is an important step to measure the reference air kerma rate of the 192Ir radioactive source and establish the measurement benchmark.