UPGRADE OF THE WIDE-ANGLE NEUTRON DIFFRACTOMETER AT THE HIGH-FLUX ISOTOPE REACTOR

The wide-angle neutron diffractometer (WAND) is an instrument that can be used either as a hat-cone geometry diffractometer or as a fast pow der diffractometer. This instrument is located at the high-flux isotop e reactor (HFIR), and is currently being upgraded. The central part of this upgrade is the development of a new curved one-dimensional posit ion sensitive detector which covers a 125 degrees angular range with a n effective radius of 71 cm. This detector will be a multi-anode (624 anodes on a 0.2 degrees pitch) He-3 gas-filled proportional counter. T his totally new system will give high resolution, good uniformity and high counting rate -a maximum capability of 10(5) cps/pixel and a 10(7 ) cps overall. A prototype of this detector has shown that these desig n targets can be met. The new WAND will greatly broaden the capabiliti es for single-crystal diffraction experiments and for time-resolved me asurements. (C) 1998 Elsevier Science B.V. All rights reserved.