Establishment and Study of Pulsed X-ray Reference Radiation Field

Research on radiation protection dosimetry mainly focuses on continuous radiation in the world, but pulsed ionizing radiation has been widely used in the fields of industrial detection, X-ray diagnosis, security inspection and scientific research. The active electronic dosimeter has been widely used in the fields of environmental monitoring, regional monitoring, personal dose monitoring and emergency monitoring. The active electronic dosimeters are calibrated in continuous radiation field, and they cannot measure short pulse and high dose rate pulsed ionizing radiation accurately. The active radiation dosimeter can be divided into G-M counter type, scintillator detector type, semiconductor detector type and ionization chamber type according to different radiation detection principles. The measurement of pulsed X-ray dose is very difficult due to its short duration and high instantaneous dose rate. Taking nanosecond radiation pulse as an example, its single pulse dose usually reaches more than 1 μSv, and the instantaneous dose rate can reach more than 105 Sv/h. For G-M counter and semiconductor detector, there are problems of measurement stacking and detection dead time, so it is difficult to achieve such a high dose-rate response, and there is an over-response problem in the instrument, which will inevitably affect the accuracy of monitoring results. The measurement of pulsed radiation dose (rate) is difficult. However, pulsed ionizing radiation has been widely used in many fields, such as the development of new detector, industrial flaw detection, X-ray diagnosis, nuclear emergency response and scientific research, etc. In this paper, the reference ionizing radiation field of pulsed X-ray was established based on steady-state X-ray machine, pulsed X-ray machine and portable X-ray machine. In order to measure the dose of pulsed reference field, the theoretical calculation, Monte Carlo simulation and experiment method were used to develop a secondary standard ionization chamber for millisecond pulsed X-rays. From the experimental data, it can be seen that the mainstream active dosimeters currently sold have low pulse dose response and even give false readings, which are not suitable for short pulse and high dose rate measurement and early warning, will cause safety trouble to personal. The dosimetric characteristics, such as pulse time, pulse dose and instantaneous dose rate were studied based on pulsed X-ray secondary standard ionization chamber and pulsed time measurement system. The lower limit and upper limit of instantaneous dose rate of the established pulsed X-ray reference radiation field are 2.5×10-3 Sv/h and 6.7×105 Sv/h respectively. Pulse time is adjustable between 50 ns and 10 s. The dose rate range of pulsed X-ray reference radiation field established in this study covers environmental level, radiation protection level, diagnosis level, treatment level, emergency level and nuclear critical accident level, which can be used to calibrate the pulsed radiation dose monitoring instrument. It is helpful to further study the pulsed radiation response characteristics of active radiation dosimeter and personal radiation dosimeter. © 2023 Atomic Energy Press. All rights reserved.