Multi-Grid detector for neutron spectroscopy: results obtained on time-of-flight spectrometer CNCS

Abstract

The Multi-Grid detector technology has evolved from the proof-of-principle\nand characterisation stages. Here we report on the performance of the\nMulti-Grid detector, the MG.CNCS prototype, which has been installed and tested\nat the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a\nside-by-side comparison to the performance of $^3$He detectors on an\noperational instrument. The demonstrator has an active area of 0.2 m$^2$. It is\nspecifically tailored to the specifications of CNCS. The detector was installed\nin June 2016 and has operated since then, collecting neutron scattering data in\nparallel to the He-3 detectors of CNCS. In this paper, we present a\ncomprehensive analysis of this data, in particular on instrument energy\nresolution, rate capability, background and relative efficiency. Stability,\ngamma-ray and fast neutron sensitivity have also been investigated. The effect\nof scattering in the detector components has been measured and provides input\nto comparison for Monte Carlo simulations. All data is presented in comparison\nto that measured by the $^3$He detectors simultaneously, showing that all\nfeatures recorded by one detector are also recorded by the other. The energy\nresolution matches closely. We find that the Multi-Grid is able to match the\ndata collected by $^3$He, and see an indication of a considerable advantage in\nthe count rate capability. Based on these results, we are confident that the\nMulti-Grid detector will be capable of producing high quality scientific data\non chopper spectrometers utilising the unprecedented neutron flux of the ESS.\n