Simulation study on diamond epithermal neutron flux detectors for BNCT

BackgroundBoron Neutron Capture Therapy (BNCT) is an advanced and precise targeted tumor treatment technology with broad application prospects. One of the core tasks in the development of this technology is the measurement of neutron flux. The primary measurement methods for neutron energy spectrum and flux in existing BNCT radiation fields are the multi-foil activation method and the Bonner sphere spectrometer method. These methods have problems such as complicated operation procedures, long measurement time, and inability to measure in real time online. Therefore, new detection technologies need to be developed urgently.PurposeThis study aims to apply Monte Carlo simulation to the design of a diamond-based epithermal neutron flux detector tailored for BNCT neutron beam measurement requirements to achieve real-time measurement of epithermal neutron flux.MethodsThe Monte Carlo simulation code MCNP5 was employed to design and optimize the detector structure, neutron response of the detector, selection of neutron conversion materials, selection of slowing materials, and high-energy neutron resonance absorption strategy. Equipped with a nuclear electronics readout system, the optimized super-thermal neutron detector was applied to real time measurement of superheated neutron flux, and performance verification of the BNCT radiation fields from accelerator neutron sources and reactor neutron sources were conducted.ResultsThe optimized design for epithermal neutron flux detector is to use a D2O sphere with a radius of 37 cm and a 0.01 cm Fe foil as the moderator and high-energy neutron absorber materials, the size of the diamond detector is 1.0 cm×1.0 cm×0.03 cm, and 6Li of 17 μm is selected as the neutron conversion layer. Verification results show that the neutron response energy range of the designed detector is 0.5 eV to 10 keV, and the uncertainty of the super-thermal neutron flux measurement results is less than 4%, which is better than the existing multi-film activation method and multi-ball spectrometer method.ConclusionsResults of this study demonstrate that designed diamond epithermal neutron flux detector can accurately complete the super-thermal neutron flux measurement of the BNCT radiation field and has guiding significance for the subsequent fabrication and testing of the detector.