Experimental verification of the simulated performance of a compact supermirror focussing device

Large gains in neutron flux on small samples are possible for long-wavelength neutrons using appropriately designed short pieces of m = 3 supermirrors in the incident beam close to the sample. These devices are particularly attractive for existing instruments on spallation neutron sources as they provide a simple method for increasing flux whilst leaving the majority of the incident beam infrastructure unchanged. This paper will describe recent results from a measurement of the performance of a two-dimensional supermirror focusing device on the SURF instrument at ISIS. Particular attention was paid to the effect of misalignment in order to obtain a quantitative measure of the precision to which such components would have to be remotely positioned in the more enclosed environment of instruments such as the SXD single crystal diffractometer at ISIS. The experimental flux gain and beam divergence are also compared with results from Monte Carlo simulations of the SURF instrument with and without the focusing device. (c) 2006 Elsevier B.V. All rights reserved.