Design of Neutron Reflectometer in the Angle-resolved Dispersive Mode for Compact Accelerator Based Neutron Sources

AbstractCompact accelerator-driven neutron sources take advantage of their readiness of operation and high adaptability to various experiments, although their neutron flux is low. We are now working on installing a reflectometer to Kyoto University Accelerator based Neutron Source (KUANS). Neutron reflectometer (NR) is one of the most simple but powerful spectrometer, in which neutron reflectivity from the surface of a sample is measured and analyzed to give so called ‘depth profile’ of the sample, which represents the distribution of materials along the surface normal direction. Usually, reflectometer requires narrow well-collimated beam. For the present reflectometer, however, incident neutron beam is narrowed at the sample position but not so much collimated to allow variety of incident angle to the sample simultaneously assuming the specular reflection at the sample surface. This multi-incident angle measurement helps to compensate weak intensity of KUANS. The motivation of this study is development of the NR with the readiness of operation for a preliminary experiment. In this study, the design of the NR is presented and the reflectivity is estimated via Monte-Carlo simulation. It was found that measurable lowest reflectivity is down to 10-2