The Neutron backscattering spectrometer IN16 at ILL—high energy resolution with high intensity and excellent signal-to-noise ratio

Abstract

Neutron backscattering (BS) spectroscopy is applied in a wide field of science where meV-energy resolution is required for the study of the dynamics in solid or soft matter, like for low frequency excitations or for accessing slow relaxations on the nanosecond (ns) time scale. BS is often combined with time-of-flight spectroscopy in order to extend the dynamic range and it is complementary to neutron spin echo in that it measures excitations directly in energy space. The BS spectrometer IN16 at ILL is now six years in regular user operation [1,2]. The success of the spectrometer is based first on neutron focusing optics, which results in a high flux [I]. second on a graphite-deflection chopper, which allows to maintain perfect backscattering conditions on the monochromator side 111, and third on an excellent signal to noise ratio combined with a nearly Gaussian resolution function [3]. New backscattering spectrometers- the NIST spectrometer, HFBS, and the planned Munich spectrometer RSSM, have adopted and extended this successful concept. We will briefly describe IN16, give examples of recent applications and will finally present some upgrade plans, which should guarantee IN 16 a bright future.