Multiplexing Capabilities of Cold-Neutron Triple-Axis Spectrometer SIKA

Abstract: SIKA, a high-flux cold-neutron triple-axis spectrometer at the OPAL reactor at the Australian Nuclear Science and Technology Organization, is equipped with a 13-blade analyser and position-sensitive detector. This multiplexing design endows SIKA high flexibility to run in both traditional triple-axis and multiplexing analyser modes. In this study, two different multiplexing modes on SIKA are simulated using Monte-Carlo ray-tracing methods. The simulation results demonstrate SIKA capabilities to work in these operational modes, especially, the multi-Q const-Ef mode. This capability was demonstrated by measuring the phonon dispersion of a Pb single-crystal sample with the multi-Q const-Ef mode on SIKA. Compared to the traditional and multi-analyser triple-axis spectrometers, multiplexing modes on SIKA combine the advantages of the high data-acquisition efficiency and flexibility to focus on local areas of interest in the (Q, w) space.