CAMEA: Guide Report

This document describes the best current candidate for a CAMEA guide made by the optimizer guide bot. The guide bot tool generates the McStas instrument and iFit files necessary for guide optimization, making it easy to investigate a large number of possibilities. The baseline requirements for the CAMEA guide is a 15 mm x 15 mm sample 0.6 m from the end of the guide, with a divergence requirement of ±0.75 degrees in the horizontal direction and ±1.0 degrees in the vertical direction. The distance between moderator and sample is 170 m. The guide does provide flux in a larger area than the requirement and at larger divergences, but the phase space illumination is only uniform within the requirement. The guide is intended to be used for the wavelength range 1.65 \AA to 6.4 \AA, but was optimized for a wavelength range of 1.0 \AA to 3.6 \AA, because experience with the optimizer shows that the results are better when optimizing for a slightly lower wavelength range than needed

A Prismatic Analyser concept for Neutron Spectrometers

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