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

点击翻译按钮获取中文摘要

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.