Recent Nuclear Data Activity at the RPI Gaerttner LINAC Center

Abstract

The nuclear data group at the RPI Gaerttner LINAC Laboratory uses a 60 MeV pulsed electron LINAC to produce short pulses of neutrons and perform cross section and other nuclear data measurements in a wide energy range from below 1 meV to about 20 MeV. This paper will cover several recent activities that are of interest to nuclear applications. Interest in thermal neutron scattering evaluations prompted the need for accurate thermal total cross section measurements for validation. To improve the neutron flux in the sub-thermal region (below 0.01 eV) a cold moderator was designed and installed. A polyethylene moderator operating at about 26 K resulted in a factor of 8 increase in neutron flux below 0.01 eV. Using this new capability, several transmission measurements were performed with samples of polyethylene, polystyrene, Plexiglas, and yttrium hydride. Neutron capture and transmission measurements in the keV energy range were made for 54Fe, which will be used in an evaluation effort that is underway. Capture measurements were collected on an array of C6D6 detectors that was expanded from 4 to 7 detectors, and a complementary transmission measurement was also performed. Finally, research aimed at experimental validation of neutron capture gamma production is in progress. Energy dependent capture gamma cascades are measured with the RPI 16-segment gamma multiplicity detector. Measurements are then compared to capture gamma cascades generated from nuclear structure evaluations processed with DICEBOX and transported with a modified version of MCNP. This system provides important information on the completeness of primary gamma-ray databases.