• Wolfgang Treimer

      Articles written in Pramana – Journal of Physics

    • A polarised SUSANS facility to study magnetic systems

      Apoorva G Wagh Veer Chand Rakhecha Markus Strobl Wolfgang Treimer

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      Using a right-angled magnetic air prism, we have achieved a separation of ∼10 arcsec between ∼2 arcsec wide up and down-spin peaks of 5.4 Å neutrons. The polarised neutron option has thus been introduced into the SUSANS instrument. Strongly spindependent SUSANS spectra have been observed over ±1.3 × 10−4 Å−1 range for several magnetic alloy samples. Spatial pair-distribution functions for the up and down-spins as well as the nuclear and magnetic scattering length density distributions in the micrometer domain, have been deduced from these spectra.

    • Neutron forward diffraction by single crystal prisms

      Sohrab Abbas Apoorva G Wagh Markus Strobl Wolfgang Treimer

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      We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater sensitivity to the incidence angle. We have measured the variation of neutron deflection and transmission across a Bragg reflection, for several single crystal prisms. The results agree well with theory.

    • Bragg prism monochromator and analyser for super ultra-small angle neutron scattering studies

      Apoorva G Wagh Sohrab Abbas Markus Strobl Wolfgang Treimer

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      We have designed, fabricated and operated a novel Bragg prism monochromator–analyser combination. With a judicious choice of the Bragg reflection, its asymmetry and the apex angle of the silicon single crystal prism, the monochromator has produced a neutron beam with sub-arcsec collimation. A Bragg prism analyser with the opposite asymmetry has been tailored to accept a still sharper angular profile. With this optimized monochromator–analyser pair, we have attained the narrowest and sharpest neutron angular profile to date. At this facility, we have recorded the first SUSANS spectra spanning wave vector transfers $Q \sim 10^{−6}$ Å-1 to characterize samples containing agglomerates up to tens of micrometres in size.

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