Preliminary shielding design of the neutron cameras for D-T fusion product diagnostics on the HL-3 tokamak

For future fusion experiments, the utilization of tritium fuel has emerged as a key consideration. For the deuterium-tritium (D-T) experimental campaign to be implemented on the HL-3 tokamak, two new neutron cameras will be developed for measuring the neutron emission profile. Owing to the intense flux of highly penetrating radiation, detector shielding is paramount to ensuring the reliability of neutron and gamma ray diagnostic systems during D -T experiments. This paper presents the shielding design of the two neutron cameras scheduled for installation on the HL-3 tokamak in 2026. The global neutron fluence was calculated by dedicated Monte Carlo particle simulation programs based on Geant4. The shielding performance of 13 candidate materials was systematically characterized, leading to the selection of borated polyethylene, stainless steel, and lead. The front, side, and collimation components of the multi-layered shield were optimized, yielding the preliminary shielding design for the HL-3 neutron cameras. For Horizontal Camera, it can provide a radiation transmissivity below 10 -4 , which satisfies the requirements of detectors. Collimation design, which determines direct particle fluence and its ratio, remains an open question.