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First data on the new ISIS muon spectrometer HiFi

Wednesday 30 September 2009

Norbornene level crossing resonance taken on HiFi

First level crossing resonance data taken on the new ISIS muon spectrometer HiFi from norbornene
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HiFi has been built as the result of a facility development grant awarded to the ISIS and Oxford University muon groups. It has an order of magnitude greater applied field than previously available on ISIS muon instruments, opening up new science areas for study using muons at ISIS. First data from the instrument is a significant project milestone, and the result of several years of effort by the team responsible for design and construction of the new instrument.

The first data taken with the new instrument is from norbornene, an organic molecular material. Muons can be used to study how the molecules of materials like norbornene move as the temperature is changed. This is done by looking at how the muons behave as the applied field on the sample is changed. At certain specific 'resonant' fields, the muon behaviour is strongly affected as the muons interact with the molecules of the material.  This results in a dip in the muon signal, as shown in the figure.  The shape of such dips and the field values that they are seen at give us information about what the norbornene molecules are doing.

As well as studying molecular motion, HiFi also opens up new opportunities for investigating magnetic materials, charge transport (for example in organic semiconductors), ionic conductors (such as materials used in novel batteries) and radical structure and reactions.

HiFi has been three years in design and construction. It is based around a state-of-the-art superconducting magnet, which generates fields up to 5 T at the sample position. The instrument is still being commissioned, but results so far show that it is working as expected from simulations carried whilst it was being designed.  It should be ready for user experiments later in they year.

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