Geometric optimization of a neutron detector based on a lithium glass–polymer composite

• Composite polymer–lithium glass scintillation detector is simulated.
• Polymer is considered to be non-scintillating in the simulation.
• Three forms of lithium glass are considered: disks, rods, and spheres.
• Glass shape has a small effect on neutron efficiency.
• Glass shape has a significant effect on gamma rejection.

We report on the simulation and optimization of a neutron detector based on a glass–polymer composite that achieves high gamma rejection. Lithium glass is embedded in polyvinyltoluene in three geometric forms: disks, rods, and spheres. Optimal shape, geometric configuration, and size of the lithium glass fragments are determined using Geant4 simulations. All geometrical configurations maintain an approximate 7% glass to polymer mass ratio. Results indicate a 125-mm diameter as the optimal detector size for initial prototype design achieving a 10% efficiency for the thermalization of incident fission neutrons from 252Cf. The geometrical features of a composite detector are shown to have little effect on the intrinsic neutron efficiency, but a significant effect on the gamma rejection is observed. The sphere geometry showed the best overall performance with an intrinsic neutron efficiency of approximately 6% with a gamma rejection better than 10−7 for 280-μm diameter spheres. These promising results provide a motivation for prototype composite detector development based on the simulated designs.