裂变伽马射线探测器的时间响应特性研究

Study on Time Response of Fission Gamma-ray Detector

根据国内首次研制出的载铀材料裂变伽马射线探测器的工作原理及其输入-输出等效电路,利用M.C建模计算的方法研究获得了探测器的灵敏体在δ辐射脉冲作用下产生并输出的脉冲电流波形g0(t),同时通过实验方法研究获得了其灵敏单元在脉冲射线作用下产生的电信号在输出电路中的时间过程gRLC(t),并最终得到了探测器的时间响应特性:响应波形前沿时间为0.72 ns,后沿时间为3.9ns,半宽为2.08 ns,探测器响应时间很快;最后通过数值计算的方法考察了探测器时间响应对不同宽度源波形的影响。结果表明:源波形时间越慢,探测器对其测量的影响就越小,其中探测器的时间响应对于半宽为100 ns的高斯型源波形的峰值、半宽、前沿以及后沿时间的影响基本上都小于0.2%,所以探测器时间响应特性完全满足这样宽度下的脉冲中子源的测量要求,对测量结果不需要进行逆卷积处理。

Fission gamma-ray detector using 235U or 238U as detection medium is a new-type detector for pulsed fission neutrons measurement,and it is developed for the first time in our country.Based on its working principle and equivalent circuit,the pulsed current g0（t） delivered from the detector＇s cathode induced by δ pulsed radiation is obtained with Monte Carlo simulation calculation.On the other hand,the pulsed current gRLC（t） delivered from the detector in output circuit is obtained from some experiments.We finally obtain the time response of the detector： rise time ～0.72 ns,fall time ～3.9 ns,FWHM ～2.08 ns,and the detector＇s time-response is very fast.The influences of the detector＇s time-response on the primary waveforms which have different time characteristics are also studied.The results show： the slower the primary waveforms,the smaller influences.If the primary waveform is Gaussian curve which FWHM is 100 ns,the influences of amplitude（A）,rise time（tr）,fall time（tf）,and FWHM（t1/2） are less than 2%.So the fission gamma-ray detector can be used to measure the rapidly changing pulsed fission neutrons,and the measurement results don＇t need any deconvolution calculations.