Abstract
This paper describes the design and operation of the Polaris time-of-flight powder neutron diffractometer at the ISIS pulsed spallation neutron source, Rutherford Appleton Laboratory, UK. Following a major upgrade to the diffractometer in 2010-2011, its detector provision now comprises five large ZnS scintillator-based banks, covering an angular range of 6° ≤ 2θ ≤ 168°, with only minimal gaps between each bank. These detectors have a substantially increased solid angle coverage (ω ∼5.67 sr) compared to the previous instrument (ω ∼0.82 sr), resulting in increases in count rate of between 2× and 10×, depending on 2θ angle. The benefits arising from the high count rates achieved are illustrated using selected examples of experiments studying small sample volumes and performing rapid, time-resolved investigations. In addition, the enhanced capabilities of the diffractometer in the areas of in situ studies (which are facilitated by the installation of a novel design of radial collimator around the sample position and by a complementary programme of advanced sample environment developments) and in total scattering studies (to probe the nature of short-range atomic correlations within disordered crystalline solids) are demonstrated.
| Original language | English |
|---|---|
| Article number | 115101 |
| Journal | Review of Scientific Instruments |
| Volume | 90 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 1 2019 |
| Externally published | Yes |
Funding
The authors would like to acknowledge the vital contribution made to this work by the late Professor Sten Eriksson (Chalmers University of Technology, Gothenburg, Sweden) who—as the holder of grants from the Vetenskapsrådet Research Council funding both the Swedish financial contribution to the ISIS Neutron and Muon Source and the postdoctoral research project of Dr. S. T. Norberg— would have been included as a co-author of this paper were it not for his untimely death before the manuscript was submitted. The Polaris upgrade project was funded by the CCLRC/STFC Facilities Development Fund, with additional financial contributions from the Swedish Vetenskapsrådet Research Council and in-kind support from The Basque Country, Spain (project led by Professor J. Bermejo). The design and construction of the instrument greatly benefitted from significant scientific, technical, and financial input from a number of collaborators, including members of the project’s Scientific Advisory Committee—Anthony Powell (University of Reading, chair), Paolo Radaelli (University of Oxford), Brian Holsman (ISIS), Colin Pulham (University of Edinburgh), Neil Hyatt (University of Sheffield), Paul Schofield (Natural History Museum, London), and Simon Clarke (University of Oxford). The design and installation of the upgraded Polaris was a major project, made possible by the efforts of numerous staff within the ISIS Electrical Engineering Group, the ISIS Mechanical Engineering Group, the ISIS Instrument Design Group, the ISIS Electrical Design Group, the ISIS Computing Group, the ISIS Electronics Group, the ISIS Detector Group, the ISIS Sample Environment Group, the ISIS Instrument Operations Group, and the Electrical and Electronic User Support Group. The authors are grateful to Ian Wood (University College London), Josh Makepeace (University of Oxford), Bill David (ISIS), Jordi Jacas Biendicho (IREC, Barcelona), and Henrik Leion (Chalmers University) for permitting the use of their research results in this paper.