Measurements of the neutron spectra from the p+Be neutron generator of the NPI CAS

The Nuclear Physics Institute of the Czech Academy of Sciences (NPI CAS) operates several neutron sources, including a generator of a continuous spectrum of neutrons up to 33 MeV. Accelerated protons from the U-120M cyclotron are directed to an 8 mm thick beryllium target to produce the neutrons. In this work, the neutron spectrum at distances of 3-8 m was directly measured with NE213 and stilbene scintillator detectors in the forward, diagonal and perpendicular directions. At a distance of 50 cm from the Be target, the neutron spectrum was validated with a gold activation detector. From previous work, the neutron spectra at close distances were characterised for use in high-intensity irradiation. Both the newly measured spectra at large distances and the previously measured spectrum were simulated using the Monte Carlo code, MCNP6.2, with ENDF7PROT and JENDL-4.0/HE nuclear data libraries. The comparison of the simulated and experimentally measured spectra revealed several limitations of both libraries.