Following the recommendations of the Facility Access Panels, the instrument scientists start to plan the schedule for the next ISIS run.
“We try to be flexible and ask users when they would like to come,” says LOQ instrument scientist Steve King. “We may find that people have to delay because samples are taking a long time to make, but if a student is finishing a PhD soon, we will try to accommodate the experiment quickly.”
One of the instrument scientists is also assigned as the local contact for the visiting team, and will discuss the experiment in more detail. Experiments involving measurements over a range of temperatures may require furnaces or cryogenic equipment, while others might need pressure cells or an atmosphere of a particular gas.
Chris Goodway, head of the section supplying pressure, furnace and gas-handling systems, says: “We like to know the requirements before the experiment is scheduled so that we can ensure we have the equipment available.” He and his colleagues also look after the equipment while in use, instructing the users if necessary, and remaining on-call during the experiment.
Sometimes a new piece of kit has to be specially designed and made in the ISIS machine shop. Jim Buckel, who specialises in machining small components, often has to make special sample-holders for users, for example, a narrow cell to contain a liquid. “Scientists tend to provide ‘fag-packet’ drawings of what they want,” he laughs. “One scientist wanted a crystal to be suspended in the beam without anything touching it. Using pictures, we established how to achieve what he wanted.” Jim says he’s machined a vast array of materials from plastic to gold, including preparing samples of “weird and wonderful” alloys used in aircraft wings.
Scientists usually prepare their samples in advance of the experiment. For Peter Griffiths’ research, this might include deuterated water and polymers. Many standard deuterated compounds are commercially available but more particular materials need a specialist supplier or in many cases to be made to order.
“We try and do as much sample preparation beforehand as we can,” says Peter. “Usually there’s a period of frenetic activity in the week leading up to the experiment. The polymers may take a few hours to dissolve; we prepare the samples for the first day’s measurements the day before so they are reasonably fresh.”
To obtain some of the mucin samples, Peter and his team had to extract material from the lining of pigs’ stomachs - “not nice material to work with”, he says. Deuterated versions of the polymers were mixed with mucin in deuterated water such that the SANS experiments would highlight the structure of the mucin in the presence and absence of the polymer so as to probe any changes in its structure. The rest of the samples were then prepared on-site using sample-preparation laboratories at ISIS.
The facility has five laboratories for preparing samples. New facilities are being built for TS-2. One lab is dedicated to the needs of biological experiments.
Jennifer Riesz from the University of Queensland preparing samples of melanin precursors for study on the Tosca instrument
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“We can help with biological sample preparation issues including working with users to express and prepare biomolecules in bacteria on a large scale, or just helping out with choosing the right sample cells,” says Cameron Neylon, whose role is to help biologists to carry out neutron experiments successfully.
“We are also available to help with making sure samples are appropriate for neutron scattering experiments. Many biological experiments aren’t as successful as they should be due to issues with sample concentration or purity. SANS in particular requires high concentrations and very good sample homogeneity and we can help to get that right," Cameron comments.
All samples and sample environments for experiments have to be evaluated for safety, and this is carried out by Steve Roberts, support laboratories manager. “We look at the standard chemical properties such as toxicity, flammability and corrosiveness, and whether special sample-handling equipment is needed,” he says.
The user has to fill in a COSHH (Control of Substances Hazardous to Health) form, and, if necessary, Steve advises on the correct way to handle and transport the material. Another important aspect is radiological safety. A neutron beam can induce radioactivity in samples, and the potential for this is considered.
The User Office
At the ‘creature-comfort’ end of preparing for an ISIS experiment are the ISIS User Office staff, who regularly check the experiment scheduling in the online proposal system and send out emails to visiting groups confirming experiment dates and reminding them to send back the COSHH form together with their accommodation and travel requirements. Accommodation is available on site at Ridgeway House or off-site at the Cosener’s House in Abingdon.
Next: Support along the way