Abstract
Boron Neutron Capture Therapy (BNCT) is known to be a new promising cancer therapy suppressing influence against normal cells. In Japan, Accelerator Based Neutron Sources (ABNS) are being developed for BNCT. For the spread of ABNS based BNCT, we should characterize the neutron field beforehand. For this purpose, we have been developing a low-energy neutron spectrometer based on 3He position sensitive proportional counter. In this study, a new intense epi-thermal neutron field was developed with a DT neutron source for verification of validity of the spectrometer. After the development, the neutron field characteristics were experimentally evaluated by using activation foils. As a result, we confirmed that an epi-thermal neutron field was successfully developed suppressing fast neutrons substantially. Thereafter, the neutron spectrometer was verified experimentally. In the verification, although a measured detection depth distribution agreed well with the calculated distribution by MCNP, the unfolded spectrum was significantly different from the calculated neutron spectrum due to contribution of the side neutron incidence. Therefore, we designed a new neutron collimator consisting of a polyethylene pre-collimator and boron carbide neutron absorber and confirmed numerically that it could suppress the side incident neutrons and shape the neutron flux to be like a pencil beam.
Highlights
Boron Neutron Capture Therapy (BNCT) is known to be a new promising cancer therapy
Only nuclear reactor has been used as a neutron source for BNCT because BNCT requires a strong low-energy neutron source
Estimation of epi-thermal neutron spectrum is known to be difficult because the shape of thermal neutron spectrum is fixed for the atmospheric temperature and fast neutrons can be identified by nuclear reactions such as charged particle emission reactions, e.g., elastic scattering, and activation reactions having threshold energies
Summary
Boron Neutron Capture Therapy (BNCT) is known to be a new promising cancer therapy. Estimation of epi-thermal neutron spectrum is known to be difficult because the shape of thermal neutron spectrum is fixed for the atmospheric temperature and fast neutrons can be identified by nuclear reactions such as charged particle emission reactions, e.g., elastic scattering, and activation reactions having threshold energies. For these reasons, a neutron spectrometer is required which can measure thermal and epi-thermal neutron energy and intensity. We developed a new intense epi-thermal neutron field by using the Intense 14 MeV Neutron Source Facility (OKTAVIAN) of Osaka University for fundamental researches of BNCT [3].
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