Electron volt neutron spectrometers

Abstract

The advent of pulsed neutron sources has made available intense fluxes of epithermal neutrons (500 meV ≤ E≤100 eV). The possibility to open new investigations on condensed matter with eV neutron scattering techniques, is related to the development of methods, concepts and devices that drive, or are inspired by, emerging studies at this energy scale. Electron volt spectrometers have undergone continuous improvements since the construction of the first prototype instruments, but in the last decade major breakthroughs have been accomplished in terms of resolution and counting statistics, leading, for example, to the direct measurement of the proton 3-D Born-Oppenheimer potential in any material, or to quantitatively probe nuclear quantum effects in hydrogen bonded systems. This paper reports on the most effective methods and concepts for energy analysis and detection, as well as devices for the optimization of electron volt spectrometers for different applications. This is set in the context of the progress made up to date in instrument development. Starting from early stages of development of the technique, particular emphasis will be given to the Vesuvio eV spectrometer at the ISIS neutron source, the first spectrometer where extensive scientific, as well as research and development programmes have been carried out. The potential offered by this type of instrumentation, from single particle excitations to momentum distribution studies, is then put in perspective into the emerging fields of eV spectroscopy applied to cultural heritages and neutron irradiation effects in electronics

Direct Measurements of Quantum Kinetic Energy Tensor in Stable and Metastable Water near the Triple Point: An Experimental Benchmark

“…The DINS measurements are carried out on the VESUVIO beamline at the ISIS pulsed neutron and muon source (Rutherford Appleton Laboratory, Chilton, Didcot, UK). [30][31][32][33] In the DINS experiment we obtain, from each l-th detector, a Neutron Compton Profile (NCP) for the hydrogen nuclei, F l (y, q). These functions represent the hydrogen longitudinal momentum distribution.…”

The quantum nature of the OH stretching mode in ice and water probed by neutron scattering experiments

“…Currently, this technique is available a) Electronic mail: roberto.senesi@uniroma2.it only at the VESUVIO beam line operating at the ISIS neutron facility. [13][14][15] Measurements were carried out on ice and liquid water, in stable and metastable phases, in a wide temperature range, 269 K <T < 673 K. Experimental results showed a remarkably diverse behavior of the mean proton kinetic energy E K and of n(p) as a function of T. 4,11,12,[16][17][18] While a quantitative agreement between experiments and theoretical predictions, using independent DINS data analyses, was found for the proton momentum distributions in ice 18 and supercritical water, 19 discrepancies were reported for liquid water at room temperatures and below. Of particular significance is the excess of E K observed across the density maximum at 277 K and across the supercooled phase at 272 K, 16 whose interpretation is still the subject of debate.…”

Temperature dependence of the zero point kinetic energy in ice and water above room temperature

“…The most direct method to measure the momentum distribution is Deep Inelastic Neutron Scattering [5,6], with experimental methods mainly developed at the ISIS pulsed neutron source and following a theoretical study by Gunn et al [7][8][9][10]. This technique allows the exploration of neutron scattering as a probe of single-particle excitations in condensed matter.…”