First users on EMU, the cold-neutron backscattering spectrometer at the Australian Centre for Neutron Scattering

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Australian Institute of Physics
The cold-neutron backscattering spectrometer, EMU, one of the four spectrometers at ANSTO, received its operating licence in 2016. First spectra were obtained from measurements on laboratory standards such as polyethylene, m-Xylene and ammonia perchlorate [1]. The high energy resolution of EMU, allows dynamics in the nanosecond timeframe to be observed. This high resolution is due to backscattering from the Si (111) crystal monochromator and analyser arrays, delivering a spectrometer FWHM energy resolution in the order of 1.2 geV. EMU also features a linear Doppler drive modulating incident neutron energies over ± 31 geV. Scattered, analysed neutrons are counted in 3He LPSD arrays. By setting the Doppler driven backscattering monochromator to zero motion, elastic fixed window scans (EFW) can be performed. Changes in intensity of the analysed neutrons, with changing temperature, for example, correspond to changing dynamics in the system. Alternatively, when the incident energy is modulated, quasi-elastic neutron scattering (QENS) can be used to observe changes in the profile shape of the elastic peak. Finally, EMU can be used to observe purely inelastic scattering, such as observed in samples exhibiting rotational tunnelling. The first users have now conducted experiments on EMU in a range of disciplines. We have measured the high temperature dynamics in lead-free ferroelectrics using (QENS) [2], and investigated the long-range oxygen diffusion in an ionic conductor [3]. We have also measured water diffusion in clays using (EFW) [4]. Future work will involve developing MANTID software for data treatment and analysis, and continuing to improve the signal-to noise ratio.
ANSTO, Data processing, Scattering, Spectroscopy, Tunnel effect, Neutrons, Ferroelectric materials
Iles, G. N., de Souza, N, R., & Klapproth, A. (2017). First users on EMU, the cold-neutron backscattering spectrometer at the Australian Centre for Neutron Scattering. Paper presented to the 41st Annual Condensed Matter and Materials Meeting, Charles Sturt University, Wagga Wagga, NSW, Australia, 31st January - 3rd February 2017. (pp. 60). Retrieved from: