Energy Calibration of Scintillator Detectors in Different Neutron Diagnostic System on Tokamak

Abstract

The purpose of tokamak plasma diagnostics is to provide the necessary parameters for device protection, operation, and maintenance. It can also supply parameters for fusion physics research. As one of the main ways to diagnose nuclear fusion plasma, neutron diagnosis focuses on the detection of neutrons, produced by the D-D and D-T fusion reactions, to obtain the physical information of internal plasma. Neutron measurements are widely performed on tokamak to provide the essential information on the neutron yield rate of the plasma that is related to fusion power. Since neutron has no electric charge, neutron can’t be ionized directly by the interaction of electrons in the detection material. The interactions between neutron and nuclei, such as nuclear reaction and nuclear recoil, are used to detect neutrons. According to the front sensitive materials, neutron detectors can be divided into gas detectors, scintillator detectors, semiconductor detectors, ionization chambers and so on. Since the magnetic field surrounding Tokamak can have a magnificent influence on the performance of photo-electronic multiplier tubes (PMTs), it is necessary to employ magnetic shielding in designing detectors, thus guaranteeing the proper operation of detectors within a strong magnetic field. Although the PMTs are equipped with magnetic shielding materials by manufacturers, they can only resist the influence of geomagnetic field. Besides the magnetic shielding and neutron/gamma shielding, neutron detectors should be calibrated before used on the tokamak. Nine similar detectors were assembled and calibrated in this paper. The basic idea of processing calibration data is that we should adjust the resolution and the light response function in order to make experiment spectrum and simulation spectrum fit on the recoil proton edge. A special explication is given to the data processing of neutron calibration, followed by an analysis of its resulting light response function and by comparison with PTB’s results.