Speaker
Description
Energy resolutions of pulsed neutrons are one of the important parameters for nuclear data measurement by TOF method. The energy resolutions are a facility-specific parameters, and has been evaluated experimentally and numerically at various TOF facilities using pulsed neutrons.
KURNS-LINAC is an L-band electron linear accelerator with maximum acceleration voltage of 46 MeV established at Institute for Integrated Radiation and Nuclear Science, Kyoto University. By using a target according to a research purpose, we can use various types of particle beam sources, i.e. neutron, electron, and photon. In addition, the pulsed width of the electron beam can be easily changed. For a pulsed neutron source, a water-cooled tantalum (Ta) target as a photo-neutron target and various moderator are used. A typical neutron flight tube used for nuclear data measurement at KURRI-LINAC is installed in the direction of 135 degree to the LINAC electron beam line, and the neutron flight path from the Ta target to a sample is about 12.7 m.
In this study, experimentally evaluations for the energy resolution of pulsed neutron flux in the neutron path were carried out. The capture gamma-rays from a Ta-181 sample were measured by a BGO detector with a TOF method and the TOF spectra for well-known resonances were obtained. The energy resolution was evaluated by comparing the full width at half maximum of the Ta-181 resonances in the JENDL-4.0. In order to obtain relationships between the energy resolution and the pulsed neutron beam width, the measurements were carried out with the pulsed neutron beam width of 100 nsec, 1 μsec and 4 μsec, respectively. As the experimental results, the energy resolution of neutron energy range from 4 eV to 100 eV corresponding to each pulse width were evaluated. For example, the energy resolution at 4.28 eV (Ta-181 first resonance peak) was about 1.0 % for a pulse width of 4 μsec.