Laue diffractometer at a long pulse spallation source

The performance of a Laue diffractometer at a Long Pulse Spallation Source is illustrated by an example. The instrument is built at a thermal /= 25 Hz source and uses a neutron guide, which is 70 m long, and a wavelength band of 2 Ȧ at the position of the sample. The pulse of 2 ms of the source can be chopped to provide a variable resolution of the order δλ/λ= 1-3%. The instrument is suited for the investigation of samples with unit cell volumes of the order of 100-1000 ų at a medium time resolution. For an averaged spallation beam power of 5MW the neutron flux at the sample position is estimated to amount to φ = 3-8 x 10⁷ncm^-2s^-1, depending on the chopper speed. The performance of the instrument is demonstrated by a Monte Carlo simulation technique. Calculations with an idealised model sample focus on the peak-to-background ratio and the ability to resolve Bragg peaks.