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18 November 2002 Remanent transmission neutron polarizer
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Our goal is to develop magnetically remanent neutron supermirrors using the material combinations Fe/Si and FeCo/Si. With these we plan to build compact neutron transmission polarizers and neutron polarizers which can be operated with their magnetization oriented antiparallel to the guide field. In the latter case no spin flipper is necessary to switch to the other spin state. The supermirrors are produced by magnetron sputtering. The preparation conditions were optimized by producing series of multilayers where the sputtering parameters gas pressures, plasma power and the speed of substrate translation were varied. Neutron reflectivity and transmission were measured with the polarized neutron diffractometer TOPSI at SINQ. Stress and magnetic behavior were determined using a profilometer and a vibrating sample magnetometer, respectively. The existence of an easy axis of magnetization is caused by anisotropic tensile stress in the Fe layers. Since the stress in Si is compressive it is possible to reduce the total stress while keeping the remanence by adding the reactive gases O2 and N2 to Si. In this way it was possible to produce Fe/Si supermirrors which show polarizing efficiencies of 96% to 99%. These supermirrors having 299 layers in total, reflect spin up neutrons up to q = 0.55/nm (m=2.5) which allows for their use as transmission polarizers in Ni coated beam guides.
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Jochen Stahn and Daniel Clemens "Remanent transmission neutron polarizer", Proc. SPIE 4785, Advances in Neutron Scattering Instrumentation, (18 November 2002);

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