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8 November 2001 Neutron optics of the ILL high-flux polarized neutron three-axis spectrometer IN20B
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The three-axis spectrometer IN20 has been upgraded to enhance significantly the data collection rate in experiments using polarized neutrons to study magnetic excitations in the (higher) thermal energy range. To increase the monochromatic polarized neutron flux, a new geometry of the primary spectrometer, optimized by detailed ray-tracing simulations, has been adopted. The main ingredients are a neutron source of a diameter increased from 100 mm to 170 mm and a large double focusing monochromator, illuminated through a heavy input slit (virtual source) of adjustable width. This geometry permits to keep the background at a possibly low level while maximizing the solid angle available for monochromatic focusing. The real challenge of the project has been the new Heusler monochromator. With its active surface of 230 x 150 mm2, consisting of 75 crystal plates mounted in 15 columns, it is the largest polarizing crystal assembly ever built. In combination with the horizontally focusing analyzer of a similar design, implemented in spring 2000, the data collection rate in the polarization analysis mode has increased by a factor 30 - 50 in April 2001 as compared to the original IN20, which up to now has provided world's highest polarized neutron flux in the thermal energy range.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jiri Kulda, Pierre Courtois, Jan Saroun, Michel Thomas, M. Enderle, and P. Flores "Neutron optics of the ILL high-flux polarized neutron three-axis spectrometer IN20B", Proc. SPIE 4509, Neutron Optics, (8 November 2001);


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