Prismatic analyzer concept for neutron spectrometers

Jonas O. Birk, M. Marko, P.G. Freeman, Johan Jacobsen, Rasmus L. Hansen, C. Niedermayer, Niels Bech Christensen, M. Måsson, Henrik M. Rønnow, Kim Lefmann

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Abstract

Developments in modern neutron spectroscopy have led to typical sample sizes decreasing from few cm to several mm in diameter 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 readily be combined with advanced focussing geometries and with multiplexing instrument designs. We present a combination of simulations and data showing three different energies simultaneously reflected from one analyser. Experiments were performed on a cold triple axis instrument and on a prototype inverse geometry Time-of-flight spectrometer installed at PSI, Switzerland, and shows excellent agreement with the predictions. Typical improvements will be 2.0 times finer resolution and a factor of 1.9 in flux gain compared to a focussing Rowland geometry, or of 3.3 times finer resolution and a factor of 2.4 in flux gain compared to a single flat analyser slab.
Original languageEnglish
Article number113908
JournalReview of Scientific Instruments
Volume85
Issue number11
Number of pages6
ISSN0034-6748
DOIs
Publication statusPublished - 2014

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