Browsing by Author "Frost, CD"

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    (3)He polarization for ISIS TS2 phase I instruments
    (Elsevier, 2011-06-01) Beecham, CJ; Boag, S; Frost, CD; McKetterick, TJ; Stewart, JR; Andersen, KH; Bentley, PM; Jullien, D
    Here we report on the development of polarization analysis (PA) techniques to be employed at the ISIS pulsed neutron source second target station. Both spin exchange optical pumping and metastability exchange optical pumping techniques are being developed at ISIS to produce polarized neutron spin filters for use as neutron polarizers and analysers. We focus on the developments of a polarization solution on the LET spectrometer, including the updated design of the PASTIS XYZ coil set and single crystal silicon analyser cell. We also report on the construction of a combined polarizer/analyser solution for the WISH diffractometer. (C) 2010 Elsevier B.V.
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    Composition dependence of the in-plane Cu-O bond-stretching LO phonon mode in YBa2Cu3O6+x
    (American Physical Society, 2008-01) Stercel, F; Egami, T; Mook, HA; Yethiraj, M; Chung, JH; Arai, M; Frost, CD; Dogan, F
    An inelastic pulsed neutron scattering study was performed on the dependence of the dispersion and spectral intensity of the in-plane Cu-O bond-stretching LO phonon mode on doped charge density. The measurements were made in the time-of-flight mode with the multiangle position sensitive spectrometer of the ISIS facility on single crystals of YBa2Cu3O6+x (x=0.15, 0.35, 0.6, 0.7, and 0.95). The focus of the study is the in-plane Cu-O bond-stretching LO phonon mode, which is known for strong electron-phonon coupling and unusual dependence on composition and temperature. It is shown that the dispersions for the samples with x=0.35, 0.6, and 0.7 are similar to the superposition of those for x=0.15 and 0.95 samples, and cannot be explained in terms of the structural anisotropy. It is suggested that the results are consistent with the model of nanoscale electronic phase separation, with the fraction of the phases being dependent on the doped charge density. © 2008, American Physical Society