Polyethylene moderator optimized for increasing thermal neutron flux in the NASBEE accelerator-based neutron field

Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) at National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology (NIRS-QST) achieved thermal neutron flux of a therapeutic intensity of (1.75 ± 0.13) × 109 cm−2 s−1 by optimizing polyethylene (PE) moderator in the beam port. The dose contamination of gamma rays was 2.37 × 10−12 Gy cm2 (the absorbed dose of 14.9 Gy h−1). The improved thermal neutron field at the NASBEE facility will be useful in the research and development for boron neutron capture therapy (BNCT). •We optimized the polyethylene moderator for the NASBEE beam port.•The thermal neutron flux was improved 1.75 × 109 cm−2 s−1 in NASBEE facility.•The gamma ray dose contamination was 2.37 × 10−12 Gy cm2.