Time-of-Flight Measurements for Low-Energy Components of 45-MeV Quasi-Monoenergetic High-Energy Neutron Field from ${^7{\rm Li}({\rm p}, {\rm n})}$ Reaction

A quasi-monoenergetic neutron field generated in the ${^7{\rm Li}({\rm p}, {\rm n})}$ reaction consists of a high-energy monoenergetic peak and a continuum to the low-energy region. In this study, the spectral fluence of the continuum was measured with the time-of-flight (TOF) method using a ${^6{\rm Li}}$ -glass scintillation detector and an organic liquid scintillation detector for the keV and MeV region, respectively. The neutron spectral fluence was determined down to the keV region by implementing a new beam chopping system and the results showed that the neutrons that came directly from the target had a lower energy limit about 100 keV. Discussions were made also on the effect of the time-independent neutrons which are assumed to be room-scattered neutrons. The obtained information is expected to contribute to understanding the quasi-monoenergetic high-energy neutron field and improvements of calibrating neutron detectors in the field.