Design of a compact long counter with an improved response using multiple point-like thermal neutron counters

A long counter with multiple point-like thermal neutron counters positioned in a cylindrical neutron moderator was investigated to improve the performance of the long counter, including flatter fluence response in a wider neutron energy range and also the compactness. The summation of the weighted counts of each thermal neutron counter yields the response of the long counter. In this study, silicon carbide (SiC) coated with 6 LiF convertor was used as the thermal neutron counter. In a further effort to balance the performance and structural complexity of long counters with multiple thermal neutron counters, the number and positions of these counters were first studied and optimized. As a result, the long counter with four specially positioned SiC counters showed the best performance. Besides, we also implemented a copper annular into the moderator to compensate for the long counter’s response above a few MeV. The response function was relatively flat in the energy range from 10 eV to 25 MeV, with a relative standard deviation of approximately 1.78%. In addition, the proposed detector can evaluate the neutron energy, allowing it to monitor neutron fluence and neutron energy simultaneously.