Calibration of the gamma-ray measurement procedure in the EAST neutron activation system

Abstract

A neutron activation system based on pneumatic transfer system has been employed to measure the time-integrated neutron yield for the Experimental Advanced Superconducting Tokamak (EAST). Those DD neutrons were detected by indium with the reaction of In115(n,n') In115m, the energy threshold of the reaction was 0.3 MeV which was capable of eliminating the interference of scatting neutrons. A small amount of DT neutron generated by the deuterium plasma was detected by silicon with the reaction of Si28n,pAl28, the energy threshold was 4 MeV so as to discriminate the DD neutron from DT neutron. The γ spectrum of activated samples was obtained with high purity germanium spectrometer. The efficiency for the measurement of fusion neutrons were calibrated by DD/DT neutron accelerator. The key coefficients using to calculate the neutron flux by characteristic γ peak counts have been obtained in this calibration. Furthermore, investigation of the thickness of samples in order to cover the wide range of neutron yields was performed. The neutron activation system was implemented to the measurement of fusion neutron yield in EAST from the experiment campaign of 2018, and obtained a linear with deviation less than ± 10% comparing with fission chamber.