Simulation study of a high-efficiency diamond thermal neutron 3D detector with double-conversion layer

Diamond is commonly employed as a semiconductor material for thermal neutron detectors due to its excellent properties such as high-temperature resistance and superior irradiation hardness. In this paper, the diamond thermal neutron detectors (DTND) were simulated using the Geant4 Monte Carlo simulation toolkit. The different types and numbers of conversion layers and the structure of the DTND were optimized by comparing the simulation results of the deposit energy spectra and the detection efficiency. DTND with a double-conversion-layer planar structure, using both ⁶LiF and ¹⁰B, can boost detection efficiency from 4.4 % to 7.2 %, overcoming the limitations of the reaction probabilities of a single-conversion layer (⁶LiF or ¹⁰B). Furthermore, for the 3D structure, the relationship between the trench spacing, the trench width, and the detection efficiency was established by integrating extensive simulation data from single- and double-conversion-layer trench-type detectors. Ultimately more than 70 % detection efficiency was obtained on a structure with a dual-sided, double-conversion layer at a trench depth of 100 μm. Our work provides valuable instructions for practical engineering applications of DTND.