DEVELOPMENT OF HIGH ENRGY RESOLUTION SPECTROMETER FOR NEUTRONS WITH PROPORTIONAL COUNTER Si DETECTOR TELESCOPE TYPE

研制了一种用于等离子体温度诊断的新型快中子谱仪，它由甲烷正比计数器和硅半导体探测器组成。为此，有许多类型的快中子谱仪，包括天然钻石探测器。采用反冲质子望远镜式光谱仪时，如果不对损失进行测量和补偿，中子-质子转换器中质子的能量损失会降低中子的能量分辨率。我们采用正比计数器气体作为转换器，可以测量气体中一个反冲质子的能量损失DE1，具有很好的能量分辨率。质子在正比计数器部分和硅探测器之间的甲烷气体死区中损失能量dE_2，在硅探测器中偏离中心一段距离的剩余能量Er，以避免直接中子辐照的辐射损伤。反冲质子的能量Ep由上述三个能量损失之和表示：Ep=DE1+dE_2+Er。中子能量En由En=Ep/cos^2rit.其中Ritaa是一个反冲质子角，可以通过知道与观测能量损失De_1对应的几何距离L来确定：L=*^&lt；De_1&gt；_{1/(De/Dx)}De。以前报道的能量分辨率为2.1%，通过设置窄的准直器布置，大大提高了能量分辨率，对14.1 MeV中子的能量分辨率和探测效率分别为1.7%和0.8×10^~(-6)。这一解决方案是迄今为止报道的最好的价值。

A new type of fast neutron spectrometer composed of a CH_4 proportional counter and a Si semiconductor detector was constructed for plasma-temperature diagnostics. There are many types of fast neutron spectrometers for this purpose, including natural diamond detector. When they adopt recoil-proton telescope type spectrometer, the energy loss of protons in the neutron-proton converter deteriorates the energy resolution for neutrons if they do not measure and compensate the loss.We adopted proportional counter gas as a converter with which we can measure the energy loss dE1, with good energy resolution, of a recoil-proton in the gas. The proton loses the energy dE2 in the dead space of CH_4 gas between the proportional counter part and Si-detector, and the remaining energy Er in the Si-detector which is off-centered by a distance to avoid radiation damage by direct neutron irradiation.The energy Ep of a recoil-proton is expressed by the sum of the above three energy loses : Ep=dE1+dE2+Er. The neutron energy En is then obtained by En=Ep/cos^2rheta.where rhetais a recoil-proton angle which can be determined by knowing the geometrical distance L corresponding to the observed energy loss dE1 as follows : L=*^<de1>_{1/(dE/dx)}dE.The loss dE2 is also calculated by knowing dE1. We reported the energy resolution to be 2.1% before, which has been greately improved by setting the narrow collimator arrangement.The energy resolution and the detection efficiency for 14.1MeV neutrons were 1.7% and 0.8*10^<-6>, respectively. The resolution is the best value reported so far.