22 Jul 2009



LET is a cold neutron multi-chopper spectrometer for the study of dynamics in condensed matter to understand the microscopic origin of material properties.


​​​​​​​​​Inside the LET detector tank


Important news for proposals in October 2019 round

Due to a technical problem during the July beam cycle one of the two disks on chopper 5 failed, and is not repairable. A new chopper 5 unit was due to be installed in January 2020 however, and we are able to run a few of the scheduled experiments for autumn 2019 with just one of the chopper 5 disks running. However there will be a significant backlog of experiments that cannot not be run until the chopper is replaced. This means that the time available on LET in the coming proposal round will be reduced compared to normal. However we are still accepting proposals, and are confident that high-quality proposals will still get beamtime. If you have any questions please do not hesistate to contact the instrument scientists, David and Rob, who will be able to offer guidance on your proposal.


The study of dynamics in condensed matter with inelastic neutron scattering provides one of the most exacting tests of the understanding of the microscopic origin of the material properties, particularly when combined with powerful computer modelling techniques now being pioneered.

The ability to make quasi-elastic and inelastic measurements over a wide dynamic range from 0.5-30 meV on a single spectrometer is quite unique. Combined with position sensitive detectors covering scattering angles from 5° to 140°, LET is having a considerable impact in many disciplines including bio-materials, polymers, magnetism and quantum fluids.

Example applications

  • Quantum fluids
  • Magnetism
  • Polymers and bio-molecular materials


LET uses a coupled cold Hydrogen moderator. Two sets of fast counter-rotating disc choppers are used to monochromate the incident beam.​

Polarized neutrons

LET now supports uniaxial (Z-only) polarisation analysis following the installation of a supermirror polariser and 3He spin filter analyser. Two key features of the polarised mode are full access to the LET detector, and rapid changeover between unpolarised and polarised modes (approx. 3 hours). Due to current limitations on 3He production polarised experiments are limited to a maximum of 5 days and must be discussed with the LET instrument scientists well in advance of proposal submission (not doing so risks the proposal being rejected on technical grounds). Currently only a standard orange cryostat and 'hot stick', covering the temperature range 1.6 - 500K, are available for use with the polarised mode.

Did you know?

LET uses the world's first 4 m long position-sensitive helium detectors.​

Instrument links: 

Contact information for the LET instrument

Location and contact information for the LET beamline

​01235 567126