The Mushroom neutron spectrometer

Abstract This paper presents a concept for a new type of in-direct time of flight cold neutron spectrometer called Mushroom. Mushroom has a unique pyrolytic graphite (PG) analyser/position sensitive detector geometry enabling a massive 2 π steradians of continuous position sensitive detector coverage, emulating some of its direct geometry counterparts such as IN5 or LET. It has many advantages over its direct geometry cousins though, being much more compact and much less expensive to build, but its biggest advantage is the order of magnitude larger count rates for the same resolution. It is envisaged it will be used to map out the 4 dimensional S ( Q , ω ) of single crystals in a matter of hours rather than days. Its design is aimed at minimising background and also uniquely allows easy selection of analyser reflection order PG002 or PG004. This paper presents details of the design along with full simulations of its potential performance using ray tracing software.