Bochum 2018 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 11: Fundamental Symmetries I
HK 11.6: Talk
Monday, February 26, 2018, 18:00–18:15, HZO 100
Investigation of non-depolarizing neutron guide coatings for neutron beta decay studies with PERC — •Alexander Hollering1, Thorsten Lauer2, Bastian Märkisch3, and Ulrich Schmidt4 — 1FRM-II TU München, 85748 Garching — 2Movatec GmbH, 85386 Eching — 3TU München, 85748 Garching — 4Universität Heidelberg, 69120 Heidelberg
Neutron beta decay is a sensitive tool to search for non-V-A couplings beyond the Standard model in the charged weak interaction. The PERC instrument is currently under construction at the MLZ, Garching and aims to measure correlation parameters in neutron beta decay with an accuracy improved by one order of magnitude to a level of 10−4. This requires control of the neutron polarization on the same level. Inside PERC instrument, an 8 m long neutron guide is used as decay volume in a magnetic field of 1.5 Tesla and is fed by a highly polarized cold neutron beam. Supermirror neutron guides are usually made of hundreds of layers from nickel and titanium on a glass substrate. Nickel is magnetized by the magnetic field which leads to depolarization of the neutron beam even for layers made of nickel alloy with vanadium added. In order to ensure a depolarization of the neutron beam on the level of 10−4 per bounce, completely non-magnetic coatings preferably made of diamagnetic materials are required. We present measurements of our supermirrors made from copper and titanium layers with excellent reflectivity. Also despite the high mobility of copper, which leads to interdiffusion, our supermirrors are highly resistant to baking-out needed to reach low residual gas pressure.