Abstract: A portable X-ray irradiation device for on-site calibration of fixed x and γ-ray radiation dosimeters has been developed by the Division of Radiation Metrology of China Institute of Atomic Energy. Firstly, the Monte Carlo method was used to establish the model and optimize the structure of the beam collimating aperture. Then, the reference radiation field range, uniformity and scattering radiation were simulated and verified by the TW32005 ionization chambers. The results show that the optimized aperture can effectively reduce its weight while meeting the requirements of beam collimating. The characteristics of portable X-ray reference radiation field meet the requirements of relevant standards. The portable X-ray reference radiation field characteristics meet the requirements of GB/T 12162.1. The correctness of the model and the effectiveness of the Monte Carlo method in the study of the characteristics of the portable X-ray reference radiation field are verified. The energy range of the radiation field is 60-164 keV, the air kerma rate is 0.08-565 mGy/h, and the ambient dose equivalent rate is 0.13-892 mSv/h. The result lays the foundation for the follow-up study of the on-site calibration technology using the portable X-ray irradiation device.

Key words: portable X-ray irradiation device, beam collimating aperture, reference radiation field, Monte Carlo