光电倍增管对14 MeV脉冲中子的直照响应

 采用ING-103型DPF脉冲中子源产生的14.1 MeV脉冲中子对EMI两个不同型号的光电倍增管EMI-9815B和EMI-9850B进行了直照实验。针对DPF脉冲中子源产生中子脉冲的同时也会产生X射线脉冲的特点，采取了飞行时间法及吸收衰减法来消除X射线对中子脉冲的干扰。利用中子及X射线速度的差异，将光电倍增管放置在离源较远的测点位置，测得了X射线脉冲和中子脉冲时间上错开的双峰波形。通过在辐射通道内添加5 cm厚的铅吸收体有效地抑制了X射线峰，在离源较近的测量位置测到了干净的脉冲中子波形。根据实测波形，得到的光电倍增管EMI-9815B和EMI-9850B中子直照灵敏度分别为10^-13与10^-15量级，该结果与理论计算结果在量级上一致。

Response of photomultiplier tube to 14 MeV pulse neutron irradiation

The response of photomultiplier tube(PMT) to scattered neutron and gamma ray is a severe interfere factor in low sensitivity scintillation neutron detection system.The response waveforms of PMT to 14.1 MeV pulse neutron is measured upon the ING-103 DPF pulse neutron source system,using two different types of PMT(EMI-9815B and EMI-9850B).To ensure the DPF source produce pulse neutron and X-ray simultaneously,it is essential to eliminate the X-ray's interference.Through time of flight(TOF) method,the neutron and X-ray pulse are separated because of their different arriving time at the ulterior detection point.The net neutron pulse is detected by adding a Pb absorber in the beam channel to restrain the X-ray.The experimental sensitivity of the EMI-9815B and EMI-9850B are 10(-13) and 10(-15) magnitude,respectively,is agreed well with the calculational results by MCNP Monte-Carlo program.