刊名:Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
出版年:2016
出版时间:1 December 2016
年:2016
卷:838
期:Complete
页码:33-38
全文大小:1671 K
文摘
An ideal solid-state supermirror (SM) neutron polarizer assumes total reflection of neutrons from the SM coating for one spin-component and total absorption for the other, thus providing a perfectly polarized neutron beam at the exit. However, in practice, the substrate's neutron-nuclei optical potential does not match perfectly that for spin-down neutrons in the SM. For a positive step in the optical potential (as in a source">Fe/SiNx SM on source">Si substrate), this mismatch results in spin-independent total reflection for neutrons with small momentum transfer source">Q, limiting the useful neutron bandwidth in the low-source">Q region. To overcome this limitation, we propose to replace source">Si single-crystal substrates by media with higher optical potential than that for spin-down neutrons in the SM ferromagnetic layers. We found single-crystal sapphire and single-crystal quartz as good candidates for solid-state source">Fe/SiNx SM polarizers. To verify this idea, we coated a thick plate of single-crystal sapphire with a source">m=2.5source">Fe/SiNx SM. At the T3 instrument at the ILL, we measured the spin-up and spin-down reflectivity curves with source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0168900216309469&_mathId=si0044.gif&_user=111111111&_pii=S0168900216309469&_rdoc=1&_issn=01689002&md5=97806337ac7d64b7b750006607b71b22">source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0168900216309469-si0044.gif"> neutrons incident from the substrate to the interface between the substrate and the SM coating. Results of this experimental test are in excellent agreement with our expectations: the bandwidth of high polarizing power extends significantly into the low-source">Q region. This finding, together with the possibility to apply a strong magnetizing field, opens a new road to produce high-efficiency solid-state SM polarizers with an extended neutron wavelength bandwidth and near-to-perfect polarizing power.