The analysis of X-Rays dose distribution in the 350 keV/10 mA electron beam machine (EBM) acility using PHITS computer code

Abstract

The EBM 350 keV/10mA is an electron irradiation facility located at the Centre for Accelerator Science and Technology (PSTA). The EBM generates the electrons with energy of 350 keV and the beam current of 10 mA. This generated electron beam can induce x-rays radiation when passing through materials. It is dangerous for workers if the radiation dose exceeds the dose threshold. The previous study has investigated the x-rays radiation in the EBM facility. However, it implemented an analytical approach and applied the high-Z material tabulation data for the x-rays source definition. In this work, we present a different approach using particle transport simulation. The Particle and Heavy Ion Transport code System (PHITS) was utilised to obtain the x-rays source data as well as its dose distribution in the EBM facility. Based on the PHITS simulation, the x-rays are induced by the interaction between electron beams and the EBM’ window through atomic fluorescence and bremsstrahlung mechanism, with the total reaction rate density of 2.6437 × 1013 reactions/cm3s. The x-rays’ maximum dose rate of 1.4659 × 104 µSv/s is located around the window, and it decreases along with the position from the window. The x-rays dose rate in the preparation room (12 m away from the x-rays source, behind 45 cm concrete wall) was 7.4975 × 10−2 µSv/s. It exceeded the permissible dose threshold. Therefore, a radiation shield or the working-duration limits is required for the workers’ safety.