A Prismatic Analyser concept for Neutron Spectrometers

TL;DR

This paper introduces a prismatic analyser concept for neutron spectrometers that enhances energy resolution and flux by using distance collimation and multiplexing, demonstrated through simulations and experimental data.

Contribution

The paper presents a novel prismatic analyser design that enables simultaneous multi-energy reflection and improved performance in neutron spectroscopy.

Findings

Achieved approximately 2x finer energy resolution.

Realized a 1.9x flux gain over traditional Rowland geometries.

Demonstrated the technique's effectiveness with experimental data from a prototype.

Abstract

A development in modern neutron spectroscopy is to avoid the need of large samples. We demonstrate how small samples together with the right choice of analyser and detector components makes distance collimation an important concept in crystal analyser spectrometers. We further show that this opens new possibilities where neutrons with different energies are reflected by the same analyser but counted in different detectors, thus improving both energy resolution and total count rate compared to conventional spectrometers. The technique can be combined with advanced focusing geometries and with multiplexing instrument designs. We present a combination of simulations and data with 3 energies from one analyser. The data was taken on a prototype installed at PSI, Switzerland, and shows excellent agreement with the predictions. Typical improvements will be 2 times finer resolution and a factor 1.9 in flux gain compared to a Rowland geometry or 3 times finer resolution and a factor 3.2 in flux gain compared to a single flat analyser slab.