Neutron Polarization On The 10-4 Level C. Klauser1, 2 , T. Bigault1, P. Böni 3, 4, J. Chastagnier1, P. Guimera-Millan1, D. Jullien1, N. Rebrova 5, M. Schneider 4 and T. Soldner1 1 Institut Laue-Langevin, Grenoble, France 2 Atominstitut TU Wien, Austria 3 E21, TU Munich, Germany 4 Swissneutronics, Switzerland 5 University of Heidelberg, Germany 1

Neutron Polarization Supermirrors Helium Spin Filter Goal: Control polarization of large, cold neutron beam with 10-4 accuracy Supermirrors Large wavelength acceptance Time-constant performance Changes beam divergence and distribution Best performance: 99.7 % polarization (crossed XSM geometry) Helium Spin Filter High polarization Conserves beam divergence Analytical description Wavelength dependence Time dependence Low transmission at high performance

The Opaque Test Bench: High Precision Analysis Polarizing/Analyzing Power 99.99 % reached AP Product Wavelength [Å] First test November 2010 at ILL, PF1B

Spin Flipper RF-Flipper

Depolarization in Polarizing Supermirrors Parameters tested: Magnetizing Field Material: Co-Ti, Fe-Si Supermirror factor m Scattering angle/wavelength Production : ILL, SwissNeutronics, Uni Mainz

Results Depolarization at low field up to 10-2 UP-DOWN FLIP DOWN-UP FLIP 350 Gauss 8000 Gauss Depolarization at low field up to 10-2 Depolarization due to misaligned domains Magnetization varies with layer thickness Similar depolarization in transmission and reflection High magnetizing field (~0.8 T) m-value: as low as possible CoTi better at low field, FeSi better at high field SuperAdam (A. Devishvili)

The Crossed Supermirror X-SM Geometry B M. Kreuz et al., Nucl. Instr. and Meth. A 547 (2005) 583. Helium cell Mirror Mirror 99.97 (1) % λ= 5.3 Å

Conclusions Opaque Helium cells: High Analyzing Power > 99.99% Diagnostic tool Opaque Test Bench Supermirrors Depolarization of all samples strongly influenced by magnetizing field Present in reflection and transmission, influence by wavelength/angle Increased X-SM performance by one order of magnitude to 99.970 (3) % Flipper Flipping efficiency > 99.99 % measured All essential components for polarized neutron decay experiments were experimentally proven to perform in a satisfactory way on the 10-4 level 1491- SO 1058/1-1 MERCI: Didier Berruyer, Thierry Bigault, Peter Böni, Jérémie Chastagnier, Pierre Courtois, Anton Devishvili, Pilar Guimerá Millán , David Jullien, Thorsten Lauer, Pascal Mouveau, Sasha Petoukhov, Natalyia Rebrova, Antonello Rizzo, Christian Schanzer, Torsten Soldner