Three-Axis Spectrometer group (TAS)

The instruments of the Three-Axis Spectrometer group of the Institut Laue-Langevin are dedicated to measuring the dynamics of microscopic matter waves in arrays of atoms in single crystals and the analogous excitations of magnetic spins in exotic materials.
These spectrometers measure the inelastic scattering of neutrons by the sample. The name "three-axis spectrometer" comes from the fact that the monochromator, sample and analyser can each be aligned independently.

Three-Axis Spectrometers

The Three-Axis Spectrometer (TAS) was invented en 1952 by the Nobel prize winner B.N. Brockhouse. It uses an analyser crystal to measure the energy of neutrons scattered from the sample. This then can detect that the neutron wavelength (energy) has changed during the scattering process, in contrast to a diffractometer which measures all neutrons scattered by the sample with no distinction.

It is primarily used for coherent inelastic scattering measurements, i.e. in studies of crystal excitations (phonons, magnons).

TAS instruments at the ILL are installed on hot, thermal and cold neutron beams to cover an energy and resolution range as large as possible.

  • IN1 - hot neutrons
  • IN8, IN20 and IN22 (CRG)- thermal neutrons
  • IN12 (CRG) and Thales - cold neutrons