Anne Terry of ISIS with members of the University of Oxford Silk Group during an experiment on LOQ to study spider silk proteins
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ISIS has dedicated instruments suitable for a wide range of experiments.
ISIS currently has over 30 neutron and muon instruments which provide diverse and complementary information on samples. These include diffractometers designed to analyse atomic-level structures, and reflectometers for studies of surfaces and interfaces. A suite of spectrometers measuring the energies of scattered neutrons provides rich information about atomic motions and magnetic and electronic behaviour in advanced materials.
Small angle neutron scattering with LOQ
About 40 different research groups carry out an average of 80 experiments a year on the SANS diffractometer LOQ - of which Peter Griffiths’ team is one.
LOQ is relatively simple, consisting of a 11-metre evacuated beamline down which the neutrons fly towards the sample. Once scattered by the sample, they hit a fixed two-dimensional detector, 4 metres away, which can detect the positions and times of arrival of the impinging neutrons. “The advantage,” says Richard Heenan one of the scientists responsible for the instrument, “is that you can probe a large range of distances in the samples in a single measurement.”
ISIS instruments are continuously being upgraded. This is carried out in partnership with the user community who will always aim to stretch instrument capabilities to their limit.
Target Station 2
Target Station 2 is ideal for the study of complex materials at longer length-scales up to a micrometre, for example, large protein assemblies in cell membranes. Neutrons are produced by the proton pulses hitting a tungsten target surrounded by novel solid-hydrogen/solid methane moderators which slow the neutrons down in just the right way. Harry Jones has been responsible for project-managing the construction of TS-2, including all the civil engineering. “We had to learn how to move a ‘mountain’ to put up the building, as well as designing and building the proton beamline, target station, neutron beamlines and instruments, but it’s gone to budget and schedule,” he says.
The Second Target Station will feed seven new instruments, although with more to be added over coming years. One of the first is a new state-of-the-art SANS instrument, designed by Richard Heenan in conjunction with the user community to measure over an even wider range of distance scales. It will provide spectacular gains for researchers studying soft matter, complex materials and biological samples.
"The increased flux and resolution of TS-2 will enable us to study even more challenging systems, in particular to probe the dynamics of self-assembly processes. This is a great and much needed boost for UK science," says Peter Griffiths.
Two 1-metre square detectors can be independently moved inside a 13-metre-long vacuum tank according to experimental needs.
The Sans2d vacuum tank arriving at ISIS
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Project engineer, David Turner, turned the scientists' sketches and specifications into reality, drawing up detailed engineering drawings and arranging manufacture. “One of the technical challenges was maintaining a vacuum between the moving sections of beam collimation in front of the sample. We came up with inflatable vacuum seals, based on those used in aircraft doors, that close up the gaps between the moving parts,” he comments.
Once the design and manufacture were completed, the installation team took over. ISIS engineer Jeremy Moor works on instrument installation. “The layout starts from the location of the sample and the floor is marked out from designer’s drawings”, he says. “We work with the drawing office and ‘heavy gang’ in building a whole beam-line and instrument from scratch.”
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