An accelerator-based neutron source design with a thermal neutron port and an epithermal neutron port for boron...

This study presents a compact accelerator-driven neutron source design with a thermal neutron port and an epithermal neutron port for Boron Neutron Capture Therapy (BNCT), based on 10 mA 2.5 MeV protons bombarding on a 100 μm thick disc-shaped Li target with a diameter of 10 cm. The moderator consists of 2 parts, the epithermal neutron moderator and the thermal neutron moderator. The epithermal neutron moderator is made of MgF₂, and the epithermal neutron port is oriented at 45° with respect to the proton beam direction, the thermal neutron moderator is composed of polyethylene (PE) and heavy water, and is positioned at 90° with respect to the proton beam direction. The in-air beam characteristics at both neutron ports comply with the recommendations of the International Atomic Energy Agency (IAEA) for epithermal neutron and thermal BNCT radiation fields, respectively. The modified Snyder head phantom is used for the in-phantom study. It is shown that the thermal neutron flux at the thermal port peaks at the skin, and the thermal neutron flux at the epithermal port has a maximum value at a depth of approximately 3 cm in the head phantom. The photon equivalent dose and the photon-isoeffective dose are employed to evaluate the dose distribution at the epithermal neutron port. The photon-isoeffective dose shows 35%-15% lower value than that calculated by the photon equivalent dose in the treatment region, and the advanced depth, double dose depth and triple dose depth calculated by the photon-isoeffective dose are shorter than these calculated by the photon equivalent dose.