Advances in Neutron Science Instrumentation at the Los Alamos Neutron Science Center (LANSCE)

摘要

The Lujan Neutron Scattering Center within the Los Alamos Neutron Science Center (LANSCE) develops instrumentation in support of research employing neutrons to investigate issues of interest to its user community. The Spectrometer for Materials Research at Temperature and Stress (SMARTS) neutron diffractometer is optimized for the study of engineering materials. SMARTS automated sample positioning and data collection system concept: The system makes use of a pair of digital theodilites, a 4 axis sample positioning stage, the SolidWorks CAD software with a custom add-in program, a calibration process, and a sample setup process. The system provides automatic positioning of the test point on the sample such that the neutron beam will interest that point for data collection. When one considers that for SMARTS the samples are contained within a tank that provides a desired test atmosphere, test temperature, and the sample is loaded to the desired strain or stress by the integral tensile machine, then one can see the advantages of this automated sample positioning and data collection system. Doubling the performance of the Lujan Center cold neutron source: The Lujan center obtains its source of neutrons through the use of a Target Moderator Reflector System (TMRS). The TMRS includes a pair of targets, six moderators, beryllium reflectors, a window insert, and an instrument insert. The cold neutron moderator has a water pre-moderator sized to reduce the heat load on the LH cryogenic system to the same level as that of the MK II design so that a costly increase in cooling capability is avoided. Next a liquid hydrogen filled moderator tank is employed to create the cold neutrons. This is followed by a beryllium reflector/filter that is contact cooled to near liquid hydrogen temperature. Using this arrangement, and maintaining the same particle beam parameters as for the MK II design, the cold neutron performance is increased by a factor of two.