Improvements in Measuring Fission-Neutron Spectra at a White Neutron Source

The spectrum of neutrons emitted in fission induced by MeV neutrons is important for a wide range of applications and for testing models of fission physics. At the Los Alamos Neutron Science Center, we are developing a program to improve the experimental data base for neutron-emission spectra from fission induced by incident neutrons from 0.5 MeV to 200 MeV. These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. Parallel-plate avalanche detectors with excellent timing characteristics are being developed to identify fission in actinide samples. A large neutron-detector array is being assembled to detect the fission neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. The status of these developmental activities and preliminary tests of the components will be presented.