The final design of the supermirror guide upgrade for the high-resolution powder diffractometer (HRPD) at ISIS, which will significantly enhance the neutron flux that is incident upon the sample, has been heavily influenced by MC simulations performed using the McStas computer program. Such simulations are computationally demanding and by distributing subcomponents of the calculation over a network of several hundred desktop personal computers, controlled by the GridMP system, simulations were able to be performed in much greater detail than ever before. In fact, not only could incident flux distributions be rapidly simulated as the design was altered, but entire diffraction patterns for wellcharacterised reference materials could also be rendered. The latter calculation for zirconium tungstate accrued some 230 days of CPU time in only 2.5 calendar days. Such calculations are clearly impractical for a single processor PC.
RM Ibberson, KS Knight, L Chapon, TAN Griffin and K Shankland (ISIS)
Research date: December 2007