The TAS-IN8 upgrade: Towards the limit of a three-axis spectrometer performance

Institut Max von Laue – Paul Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France

^* Corresponding author: aivanov@ill.fr

Published online: 9 October 2023

Abstract

IN8 is a high-flux three-axis thermal neutron spectrometer designed to measure inelastic neutron scattering on single crystals in a wide energy and momentum transfer range. It is the highest thermal flux spectrometer worldwide with the monochromatic flux at the sample up to 10⁹ neutrons/cm²/s where users can perform demanding experiments not possible anywhere else. In recent years, the IN8 spectrometer has undergone several major upgrades that have further extended the capabilities of the instrument to the limits achievable with the standard setup. The first part of the upgrade was centred on the replacement of the monochromator assembly, now consisting of four double focusing reflecting crystal faces with enhanced luminosity. The ensuing upgrade was to replace the entire secondary spectrometer. As the result, the new spectrometer, called Thermes, profits from a compact design and it is well shielded against ambient experimental background. All the incorporated modifications have given the instrument an unprecedented and unique luminosity combined with an optimal signal-to-noise level and a remarkable configuration flexibility for a broad range of experimental requirements.