脉冲X射线剂量测量方法

Dose rate measurement of pulsed X-ray reference radiation field

为了解决主动式电子剂量率仪在脉冲辐射条件下的溯源需求,评估主动式电子剂量率仪测量脉冲辐射剂量的准确性,本文采用栅控技术于中国计量科学研究院建立了用于辐射防护剂量量值传递的脉冲X射线参考辐射场,具有曝光时间可调的特性。对脉冲X光管的管电压、曝光时间、脉冲上升/下降时间、辐射场均匀野大小进行了测试,同时对脉冲辐射场空气比释动能率测量方法进行了研究。研究结果如下:利用介入法示波器测量管电压,测量值与管电压预设值在100 kV时,相对偏差为0.19%。在建立的均匀辐射场中,利用电离室实现了脉冲场的空气比释动能率的测量,当管电压为60 kV,管电流为50 mA时空气比释动能率约为3 mGy/s。本文研究结果可为后续空气比释动能率定值提供参考。

A pulsed X-ray reference radiation field used for transmission of radiation protection dose value is estab-lished by using the grid control technology in the National Institute of Metrology China to meet the traceability re-quirements of active dosimeters under pulsed radiation conditions and evaluate the accuracy of active dosimeters in measuring pulsed radiation dose.This pulsed X-ray reference radiation field has the characteristic of adjustable X-ray exposure time.The tube voltage,exposure time,pulse rise/fall time,and radiation field uniformity of the pulsed X-ray tube were tested,and the measurement method of the air kerma rate of the pulsed radiation field was studied simultaneously.The results of the study are summarized below.When using the interventional oscilloscope to measure the output tube voltage,the relative deviation of the measured and preset values of tube voltage is 0.19%at 100 kV.In the established uniform radiation field,the air kerma rate measured by the ionization cham-ber is approximately 3 mGy/s when the tube voltage is 60 kV and the tube current is 50 mA.The results of this work can provide a reference for subsequent determinations of air kerma rates.