EMU, the cold-neutron backscattering spectrometer at the Bragg Institute, ANSTO
Australian Institute of Physics
The Bragg Institute is currently in the final installation stage of a cold-neutron backscattering spectrometer in the ANSTO OPAL research reactor neutron guide hall. This spectrometer, called EMU, is based on Si (111) crystal backscattering and extracts neutrons from a cold neutron guide via a double HOPG (002) crystal premonochromator setup. Backscattering occurs through implementation of spherical focusing between the Si (111) crystal monochromator and analyser arrays, aiming to deliver a spectrometer FWHM energy resolution in the order of 1.2 μeV. EMU also features a 7-metre long focusing guide located between the two premonochromators, a so-called graphite chopper alternating beam delivery to the backscattering crystal monochromator and then into the secondary spectrometer, and a linear Doppler drive modulating incident neutron energies over ± 31 μeV. Scattered, analysed neutrons are counted in 3He LPSD arrays. EMU is provisioned for future extensions of its dynamic range via higher-resolution, undeformed Si (111) crystal analyser arrays, and variable HOPG (002) crystal premonochromator reflection angles. Access to the EMU spectrometer will be via beam-time requests to the OPAL neutron-beam user facility. EMU is ideally suited for measuring relaxation times from a few 10 ps to over 1 ns, for momentum transfers up to 2 Å-1, and readily from cryogenic temperatures up to 700 K.
ANSTO, Australia, Backscattering, Cold neutrons, Crystals, Graphite, Installation, Monochromators, Neutron diffraction, OPAL Reactor, Pyrolytic carbon, Silicon ions, Spectrometers, Spectroscopy
de Souza, N., Klapproth, A., & Iles, G. N. (2015). EMU, the cold-neutron backscattering spectrometer at the Bragg Institute, ANSTO. Paper presented at the 39th Annual Condensed Matter and Materials Meeting, Charles Sturt University, Wagga Wagga, NSW, 3 February 2015 - 6 February 2015, (pp. 70). Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2015/Wagga2015_10_Handbook.pdf