Evolution of the existing instruments, and design and construction of new ones, open up fresh opportunities for materials investigations. Some of the major developments over the past year on ISIS
instruments are described here.
Merlin is the new high flux inelastic instrument at ISIS, designed to have 10-30 times the count rate of its predecessor Het. The instrument is now finished and we are awaiting beam to complete the technical and scientific commissioning. Merlin will work in an energy range similar to Maps and Het (10 – 1500 meV) and has a very large position sensitive detector bank to enable studies of magnetic or lattice excitations in crystals or powders.
The long shut-down has seen an extensive upgrade of Iris detector banks. The work has included production of new photomultiplier tube manifolds for the graphite and mica analyser banks; addition of μ-metal shielding to avoid stray-field interference from cryomagnet operation on neighbouring instruments; and improved stability by use of Gem-type detector electronics and relocation to a temperature controlled environment. Following an initial commissioning period, Iris is expected to resume its user programme later this year.
HRPD is presently undergoing a major upgrade with the installation of a high-reflectivity supermirror guide. Supermirror technology allows major flux increases in the key high-Q region (an order of magnitude more than the existing instrument) and, in addition, the increased radius of curvature of the new guide design will allow the transmission of shorter wavelength neutrons making it feasible to access even smaller d-spacings. The intrinsically high instrumental resolution, Dd/d better than 10-3 and effectively constant across the whole diffraction pattern, is retained. The old guide has been removed and preparations are underway for installation of the supermirror replacement.
Conversion of Loq from VMS/CAMAC based to PC/LabView/SECI-based control has been completed, and there is also a new XML-based format for reduced data which will be common to SANS beamlines at ILL and SAXS at Diamond. The new ‘SANS Xpress’ access mechanism has been launched, where one day of beam per cycle is available for samples sent in by post, either to obtain desperately needed results, to complete earlier work or to try new ideas. A new Anton-Paar Rheometer for Loq, and eventually for SANS2d and I22 at Diamond, is now available for users.
The motion control electronics on Surf have been upgraded to run with the new standard ISIS Galil control system, requiring a complete rewiring of the instrument. The data acquisition electronics have been upgraded to the new DAE-2 system, and the DEC alpha instrument control workstation has been replaced with a PC. Finally, the instrument control program and motor controls software are being upgraded to comply with the standards set for the new TS-2 instruments.
The Crisp reflectometer has also completed its transition to the Galil controller system. The motor control software developed during this project is providing a template for the control systems for TS-2. Crisp continues to run a diverse program of science ranging from detergency to quantum effects in liquid 3He. About 1/3 of beamtime is devoted to thin film magnetism with an increasing emphasis on off-specular scattering.
Hifi is the new high field muon spectrometer being built with funds from the Facility Development programme. The past year has seen the ordering of the main 5 T magnet from Cryogenic Ltd, with delivery expected in March 2008. Design of the instrument detector array is also almost finalised. The geometry of the array has proved a challenge, as the magnetic field strongly affects the decay positron trajectories, but prototype detectors have just been tested, and the full array should go for manufacture later this year. To make way for Hifi the DEVA spectrometer has been decommissioned, so that the EC muon facility will run with just two instruments rather than three for a period of around a year. Hifi is expected to be operational from late 2008.
The Polaris upgrade, funded through the STFC Facility Development programme with contributions from Swedish and Spanish partners, will see a complete rebuild of the instrument. Detector banks will be replaced by large solid angle Gem-type modules to give a significant increase in count rate; incident beam collimation will be improved; and an oscillating radial collimator will reduce background scattering when using complex sample environment equipment. Detailed design work is now in progress, and installation of the new instrument is provisionally planned for late 2009