Browsing by Author "Sutton, C"

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    In situ monochromator alignment on ANSTO’s thermal spectrometer, TAIPAN
    (Australian Institute of Physics, 2018-01-30) Sutton, C; Rule, KC; McIntyre, GJ; Danilkin, SA; Stampfl, APJ
    TAIPAN is the thermal triple axis spectrometer at ANSTO and also hosts an alternate secondary spectrometer called the Be-filter. Both instruments use a common graphite monochromator (PG002) to select a single wavelength or energy of the neutrons. By rotating the monochromator with respect to the incident beam of neutrons from the reactor, the energy of the neutrons from the monochromator can vary between 5-70 meV. The PG002 monochromator is made from 63 individual crystals of highly oriented pyrolytic graphite and the neutrons are scattered from the 002 lattice planes. The benefit of separate crystals is that they can be oriented to allow for vertical focusing of the neutron beam, or horizontal focusing or double focusing, depending on the experimental requirements. Recent measurements at TAIPAN have indicated that the crystals may not be well aligned on the double focusing mechanism, leading to broad peaks that indicate an increased mosaicity. We will present our work to develop a rapid in situ laser alignment-checking procedure for the 63-crystal TAIPAN graphite monochromator. Due to the small aperture, translation, rotation and tilt of the laser, as well as rotation and tilt of the monochromators would be needed, which will involve derivation of the geometrical mathematics, construction from what we have available of a stage with the large translations needed, testing ex situ, then in situ.