Mushroom will provide a huge capability boost compared to the comparable existing ISIS instrument (LET), which is frequently oversubscribed.
Technique: Low-energy indirect geometry spectroscopy
Contact: Russell EwingsWhy do we need Mushroom?
Mushroom will provide unique information on the dynamics of samples two orders of magnitude smaller than the current state of the art, giving unique input into the functional materials design process much earlier than currently possible. Mushroom will support the materials science requirements of a large range of priority areas: clean growth, hydrogen economy and quantum technologies.
What will Mushroom do?
Mushroom will enable significant acceleration in the materials discovery and utilisation process. For example, the study of barocaloric materials, ideal candidates for environmentally friendly refrigerants in cooling applications from food storage to computing.
Watch Prof Andrew Goodwin from the University of Oxford talk about the applications of Mushroom:
Technical Success Criteria
• Maximise the count rate compared to LET as much as feasible but at least x10 for same resolution
• Maximum sample size 1x1 cm (small sample spectrometer but also necessary for prismatic effect)
• Incident energy range 1 -20 meV (like LET)
• Energy resolution (PG002) not worse than 80 μeV (at elastic) as this is quite typical for LET in a common running mode (Ei=3.7meV)
• Q resolution similar to LET for Horace scans (typically ΔQx≈ΔQy≈0.07Å-1at 3meV)
• Incoming beam divergence maximum ±1.5degrees but can be controlled with jaws
• In plane detector coverage 5-170 degrees. Out of plane coverage of ±8 degrees (good for in-plane Horace scans plus for high magnetic fields and pressure cells)
• Velocity selector must not exceed 1m radius
Further information
MUSHROOM (Multi-Use Spectrometer for High Rate Observations Of Materials) is an instrument proposed under the ISIS Endeavour programme. It is an indirect geometry cold neutron spectrometer, to be built on ISIS TS-2. It is optimised for extremely high count rate inelastic neutron scattering experiments, and will offer between 20 and 70 times higher count rate than LET. Its design has been optimised for small samples, of a size more normally associated with diffraction. This will allow newly discovered materials to be studied with inelastic scattering more readily. It will allow user groups who do not have access to large samples to perform inelastic scattering experiments. It will allow extreme sample environment (high magnetic field, high pressure, electric field, uniaxial strain, etc.) to be used for inelastic scattering.
The neutrons enter via an elliptical guide (blue) and are scattered by the sample towards a large highly pixellated array of pyrolytic graphite analyser crystals (copper colour), covering ± 8 degrees out of plane and ~320 degrees in plane. The analysers select a final neutron energy of ~4.2 - 4.7 meV, and following the prismatic effect are focused on to position sensitive detectors below. Between the analysers and detectors is a neutron velocity selector composed of a large disk spinning at 30 Hz with absorbing blades around its circumference. This stops higher order reflections from the analysers, preventing spurions, and also ensures that each detector pixel only "sees" the correct small portion of the analyser array, thus reducing background.
The full MUSHROOM scientific case can be accessed here: 
MUSHROOM Detailed Science Case v1.0.pdf
Supporting detailed science case studies, covering short, medium and long term impact can be accessed here:
Case study 1 - Immediate impact - Magnetism.pdf
Case study 2 - Development opportunity - Pressure.pdf
Case study 3 - Future directions - Nanostructures.pdf
The detailed business case can be accessed here: Mushroom Business Case.pdf
A detailed technical description of the instrument can be accessed here: MUSHROOM_technical_case.pdf
