Present Status of KENS

摘要

The KENS pulsed neutron source was firstly constructed in 1980 with both of the thermal neutron moderator (H2O moderator at 300K) and the cold neutron moderator (solid methane moderator at 20 K). Since 1980, it has been operated with a 20 Hz-proton beam of 500 MeV and 2-6 mu A. In 1998, absolute measurements of the neutron fluxes were made at various neutron beam lines by a gold foil activation method as well as a fission detector. It suggested that the sub-cadmium neutron flux of the cold neutron moderator was about 30 percent of the nominal design value although the epi-thermal neutron fluxes (E > 0.5 eV; cadmium cut-off energy) were nearly equal to the nominal value. It had been considered that the flux reduction below 0.5 eV was caused by a part of cadmium-liner in the neutron beam line.