Polarization of very cold neutron using a permanent magnet quadrupole

For the future fundamental physics experiments by using cold neutrons, we are developing a device which can measure the neutron polarization degree by accuracy significantly below 10−3. A quadrupole magnet is one of the promising candidate to measure the neutron polarization degree by such extremely high precision. We have performed a polarization experiment by using the quadrupole magnets at the Very Cold Neutron (VCN) port of the PF-2 in the Institute Laue-Langevin (ILL). As a result, we obtained the polarization degree P with very high accuracy P=0.9994±0.0001(stat.)±0.0003(syst.), which meet our requirement significantly.