Design and performance of the new supermirror guide on HRPD at ISIS

The high-resolution powder diffractometer (HRPD) has been upgraded with the installation of a 100 m supermirror guide. The guide is a unique ballistic design that is elliptic in both horizontal and vertical cross-section and utilizes a graded supermirror coating of between m=1.5 in the center to m=3 at the beam entry and exit points. Flux gains are considerable when compared to the performance of the original m=1 guide. The shallower radius of curvature (36 km) of the new guide also permits transmission of short wavelength neutrons previously cut off. The flux gains have been achieved whilst retaining the high resolution at backscattering, Δd/d∼5×10−4. Results following initial commissioning studies are described highlighting the new capabilities of the instrument and new scientific opportunities resulting from the upgrade are discussed.