Design of compact neutron detector for tokamak

Most neutron spectrometers currently used in tokamak devices are based on liquid scintillators coupled with photomultiplier tubes (PMTs), which present challenges due to their large size and susceptibility to electromagnetic interference. In recent years, silicon photomultipliers (SiPMs) have increasingly supplanted traditional PMTs with their advantages, including small size, high quantum efficiency, and resistance to electromagnetic interference. This study presents a novel type of neutron detector for tokamak neutron diagnostics, in which the neutron probe consists of a liquid scintillator, BC-501 A, coupled with a SiPM array. This neutron detector can be used for neutron flux monitoring and, in combination with spectral deconvolution, also for spectrum measurements. The detector was calibrated with several isotope gamma sources, and the discrimination performance was verified on an Am–Be neutron source and the HL-3 device. Results from the Am–Be neutron source experiments indicated that the n/γ figure of merit (FOM) was 1.56 within the energy range of 200–800 keVee. Similarly, on-site experiments conducted at the HL-3 device demonstrated that the FOM was 1.61 within the same discrimination energy range. Furthermore, the measured variation in neutron intensity over time aligned closely with results from multiple neutron detectors on site. This research indicates that the newly developed SiPM-based neutron detector has preliminarily demonstrated its capability to operate on tokamak devices. The next step involves calibrating neutron energy and calculating the response matrix to facilitate spectrum unfolding.