The RITA spectrometer at Riso - design considerations and recent results

In the new cold triple axis spectrometer RITA at Riso we have improved the front end by extensive use of state of the art optical elements and better shielding material. The analyser system is situated in one large open tank and consists of seven individually orientable PC(002) crystal analyser blades, and a 170 mm by 120 mm(2) area sensitive micro-strip detector. In comparison to the old TAS6 spectrometer we have obtained a factor 2-5 gain in intensity on the sample, a substantially lower background, much more flexibility for optimising the instrument and the possibility to go beyond simple point-by-point inspection. The excellent performance of RITA in the standard TAS mode is exemplified by a study of the dynamics of approximate to 15 nm hematite (alpha-Fe2O3) nano-particles, and utilisation of horizontal and vertical focusing modes to stud; two dimensional systems is illustrated by a study of the spin fluctuations in the high T-c superconductor La1.83Sr0.17CuO4. (C) 1998 Elsevier Science B.V. All rights reserved.