Dresden 2013 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 81: Instrumentation
HK 81.6: Vortrag
Donnerstag, 7. März 2013, 18:15–18:30, WIL-A221
High Precision Neutron Polarisation with Supermirrors — •Christine Klauser1,2, Thierry Bigault1, Peter Böni3, Pilar Guimerá Millán1, Martin Schneider4, and Torsten Soldner1 — 1Institut Laue-Langevin, Grenoble, France — 2Atominstitut, Technische Universität Wien, Austria — 3Physikdepartment E21, Technische Universität München, Germany — 4SwissNeutronics AG, Brühlstrasse 28, CH-5313 Klingnau, Switzerland
Absolute measurements of correlation coefficients in neutron beta decay are presently limited to a relative accuracy in the order of 10−3 by systematics and statistics. Next-generation instruments aim for 10−4 accuracy, implying a 10−4 accuracy for the polarization of a large cold neutron beam. State-of-the-art polarizing super mirrors in the X-SM geometry deliver about 99.7% polarization only. This limitation of the performance is caused by depolarization by the supermirrors themselves. We present a systematic study of depolarizing effects in polarizing supermirrors. The highly sensitive Opaque Test Bench based on 3He spin filters is used as diagnostic tool. We have studied depolarization in both reflection and transmission for different supermirrors, varying in material and supermirror factor m, and investigated the relationship to magnetizing field, incidence angle and wavelength. The results of this study have been used to push the polarisation of the X-SM geometry to 99.970(3), combining a FeSi mirror and a CoTi bender.