Abstract
The first experimental characterization of a multiple energy analysis wide angle backend for a cold triple-axis spectrometer is reported. The multi-analyzer module MultiFLEXX employs 155 detection channels which simultaneously probe an extensive range in wavevector and energy transfer. Successful mapping of magnetic excitations in MnF2 and Ho demonstrate order of magnitude gains in data collection efficiency using this novel type backend. MultiFLEXX is competitive to standard triple-axis spectroscopy in terms of energy resolution and signal-to-noise ratio. A minority of the detector channels is affected by spurious signals inherent to this multiplexing concept. The characteristic signature of these spurious signals easily allows for their discrimination. The instrument concept focuses on detection efficiency in the horizontal scattering plane which makes it an ideal technique for fast mapping and parametric studies including extreme sample environment.
Highlights
MultiFLEXX will be operated with the standard sample environment suite available at FLEXX
The module was designed for both robustness and simplicity in operation. The latter was achieved by minimizing the amount of variable parameters: the incident energy Ei, the sample rotation angle A3 and the scattering angle A4 determining the angular position of the whole module with respect to the incident beam and the angular range covered by MultiFLEXX
The newly built multi-analyzer module MultiFLEXX for the cold triple-axis spectrometer FLEXX has been characterized in terms of its mapping capabilities, energy resolution, detection efficiency and background
Summary
MultiFLEXX will be operated with the standard sample environment suite available at FLEXX (cryostats, furnaces, cryo-magnets, pressure cells). For incident energies larger than 9 meV the background in the first channels (nominal energy 2.5 meV) increases drastically (up to 17 counts/min) due to higher-order Bragg scattering of the analyzer. To the existing sample environment suite an in-house redesign of an Orange cryostat with a very low and flat background is available. For this cryostat two important modifications of the VTI sample space have been implemented: The wall thickness of the VTI tube has been reduced to 0.2 mm in order to minimize the amount of material in the neutron beam. To guarantee a safe operation a copy of the thin walled VTI sample tube was tested to withstand pressures up to 11.5 bar before destruction
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