Powder diffraction on a long-pulse spallation source

Monte Carlo simulations have been performed for a time-of-flight monochroma tor powder diffractometer housed on a thermal moderator at a Long-Pulse Spa llation Source and for a conventional crystal monochromator instrument on a thermal moderator of a reactor source of four times the time-averaged Aux. By designing the time-of-flight instrument to utilise the inherent advanta ges of the technique whilst optimising to the peak performance of the cryst al monochromator case, the performance of the TOF-instrument is shown to ex ceed that of the reactor-based diffractometer, despite the lower time-avera ged flux of the source. Further, a simple extrapolation of the results obta ined for the pulsed-source shows that such a TOF diffractometer would out-p erform a conventional instrument if both were to be housed on the same reac tor. (C) 2000 Elsevier Science B.V. All rights reserved.