长计数器的效率刻度及其应用
Efficiency calibration of long counter and its application

为了准确测定241Am-Be 中子源的强度，研制了一套长计数器测量系统，并利用四川大学2.5MV质子静电加速器产生的单能中子在多个中子能点对其探测效率进行刻度，在刻度过程中中子注量由金活化法确定，并采用挡锥法扣除大厅散射中子本底的贡献.结果表明我们研制的长计数器在所刻度的中子能区范围内具有很好的坪特性.用该长计数器测量系统测得241Am-Be 源的强度为7.188×105/s ，不确定度为3.5%.
In order to accurately measure the strength of an 241Am Be neutron source, we developed a long counter measurement system, and calibrated its detection efficiency at several neutron energy point on 2.5 MV electrostatic accelerator of Sichuan University. The neutron fluence is determined by 197Au activation technique. We also measured the count of scattering neutrons using retaining cone method. The results show that the long counter’s detection efficiency changes smoothly as the energy changes in the calibrated neutron energy area. The strength of the 241Am Be neutron source is 7.188×105/s measured by this long counter measurement system with the uncertainty of 3.5%