CRG - Cold neutron time-focussing time-of-flight spectrometer

SHARP, the project

Following the agreement to strengthen the Franco-Swedish cooperation in the field of neutron scattering, the Laboratoire Léon Brillouin (LLB) is involved in the construction of an inelastic time-of-flight spectrometer. After the announcement of the Orphée reactor shutdown in 2020, the project originally planned at Saclay could be transferred to the Institut Laue Langevin (ILL). This renaissance takes the form of an A type CRG contract concluded on September 29th 2017 between the DRF of the CEA, the INP of the CNRS, and the ILL.

This new project SHARP (Spectromètre Hybride Alpes Région Parisienne) consists of a complete rebuilding of the IN6 secondary spectrometer: sample environment, time-of-flight chamber and detector. The work will last one year and is scheduled to be accomplished with the ILL's 2019 long shutdown. The spectrometer will be equipped with 240 position sensitive detectors (PSD) under 5 bars of 3He. Beyond the gain of a factor four in detection coverage solid angle, these new detectors will allow an essential gain in the definition and mapping of the (Q, ω) phase space.

Finally, the third improvement will concern the time-of-flight chamber itself. It will be under vacuum. A removable foil between the sample and the inlet of the chamber will enable to operate either with a sample under vacuum or under a controlled atmosphere. In the first configuration, the vacuum of the chamber also serves as the cryostat isolation vacuum. The number of windows between the sample and the detector will be minimized to offer an improvement in signal to noise performance. The second configuration will make it possible to study samples under controlled atmosphere or in complex environments, such as for laser heating or electrical excitation studies.

As part of the Phase 2 of the Endurance programme, a longer-term project (starting in 2023) would be to merge the SHARP spectrometers and the ILL RAMSES project at the end of a new dedicated guide. A bandwidth chopper positioned upstream of a horizontally and vertically focusing monochromator would also allow to combine i) an additional gain in brightness and ii) a decrease in background noise. Finally, an extended experimental area would make it possible to exploit a wide take-off angle range giving access to the entire range of incident wavelengths between 2 and 6 Å. This new high brilliance spectrometer would allow studies in extreme conditions such as at very high pressures and/or experiments on samples only available in very small quantities.

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