Nuclear data research at the Los Alamos Neutron Science Center

Abstract

The Los Alamos Neutron Science Center is based on an 800-MeV high current proton linear accelerator, which is used to produce intense pulses of neutrons over 16 orders of magnitude in energy from ultra-cold neutrons to neutrons with energies up to 800MeV. The four separate neutron production areas and the neutron energy ranges at each are: (1) the Weapons Neutron Research facility (0.1 to 800MeV); (2) the Lujan Center with moderated neutrons (cold - 500keV); (3) the Lead Slowing-Down Spectrometer (0.1eV to 200keV); and (4) the Ultracold Neutron Research facility (ultracold). Because of the flexibility of the accelerator, a wide range of neutron source intensities, pulse widths, and intensities is possible. Nuclear data measurements are conducted with the first three of these sources. Present research activities include experiments (with the instruments used) on high-resolution gamma-ray production by neutrons (GEANIE), neutron capture (DANCE), neutron and gamma-ray emission from fission and other reactions (FIGARO), charged-particle emission (NZ), neutron-induced fission (FISSION), and fission on small samples with a Lead Slowing Down Spectrometer (LSDS). With these capabilities, new approaches to studying neutron-induced reactions are yielding information on a wide range of nuclear data: gamma-ray emission including multiplicity and energy distributions, capture-to-fission ratios, transmutation reactions, emission probabilities for charged particles and neutrons, and cross sections on nuclides off the valley of stability. For some of the instruments, reactions can be studied on very small or short-lived samples. Analysis of the accuracy and precision of experiments is now being carried out in cooperation with data evaluators in order to improve the files of data covariances. Furthermore, the data are providing stringent tests of nuclear reaction models. Researchers from other laboratories in the US and from other countries collaborate in or lead many of these studies. The overview, presented here, of recent and on-going nuclear data research highlights several of the unique research opportunities made possible by the LANSCE neutron sources and specialized instrumentation. Possibilities for future advances are outlined.