A low-temperature sample orienting device for single crystal spectroscopy at the SNS

A low temperature sample orientation device providing three axes of rotation has been successfully built and is in testing for use on several spectrometers at the spallation neutron source (SNS). Sample rotation about the vertical (ω) axis of nearly 360° and out of plane tilts (φ and v) of from -3.4° to 4.4° and from -2.8° to 3.5°, respectively, are possible. An off-the-shelf closed cycle refrigerator (CCR) is mounted on a room temperature sealed rotary flange providing ω rotations of the sample. Out-of-plane tilts are made possible by piezoelectric actuated angular positioning devices mounted on the low temperature head of the CCR. Novel encoding devices based on magnetoresistive sensors have been developed to measure the tilt stage angles. This combination facilitates single crystal investigations from room temperature to 3.1 K. Commissioning experiments of the rotating CCR for both powder and single crystal samples have been performed on the ARCS spectrometer at the SNS. For the powder sample this device was used to continuously rotate the sample and thus average out any partial orientation of the powder. The powder rings observed in S(Q) are presented. For the single crystal sample, the rotation was used to probe different regions of momentum transfer (Q-space). Laue patterns obtained from a single crystal sample at two rotation angles are presented.