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Abstract: Small-angle neutron scattering technique using polarized neutrons is powerful for studying structures in the range between nm and μm of magnetic materials. In addition, they have been used for the incident beam of focusing-geometry SANS instruments using a magnetic neutron lens, where a high polarization degree of about 99.9% is necessary because the imperfectness of the neutron polarization increases the background level. We are going to install such a magnetic focusing system on the new time-of-flight SANS (TOF-SANS) instrument at the J-PARC so as to make qmin smaller than 10−3 Å−1 and improve the resolution of the conventional TOF-SANS at low q. As a polarizing device of the instrument, two V-shaped polarizing super mirrors arranged in crossed geometry to enhance the polarization degree has been considered. In this paper, we present the concept and the detailed design of this device and its performance estimated by Monte Carlo simulations. [Copyright &y& Elsevier]

Abstract: We have performed small-angle polarized neutron scattering experiments of spherical Fe16N2 nano-particles, which are potential candidate materials for high density magnetic recording tape. The results were analyzed based on a core-shell model, and we evaluated the magnetic structure of the particles. The correlation between the magnetic structure and magnetic stability of the particles were discussed in terms of high density recordings. [Copyright &y& Elsevier]

Abstract: We obtained highly polarized very cold neutrons through a quadrupole magnet with a large aperture. When neutrons go through a quadrupole magnet, parallel-spin neutrons are attracted to the magnet axis and anti-parallel-spin neutrons are repelled off the axis. Therefore, the neutrons through a sufficiently long quadrupole magnet have completely parallel-spin. At the downstream of the quadrupole magnet, we placed another quadrupole magnet to divide neutrons into two regions depending on their spin directions. We obtained the neutron polarization from the integrated count of the two regions and found it was 99.88±0.09 (stat.)±0.05 (syst.)%. [Copyright &y& Elsevier]

Abstract: We have designed and demonstrated a prototype on-beam spin-exchange optical pumping (SEOP) 3He neutron spin filter (NSF). It is designed as the incident neutron polarizer for spallation neutron sources, where the installation space is limited due to thick radiation shielding. The size of the NSF is roughly 50cm×50cm×25cm including the diode-laser optics with a frequency narrowing external cavity, and a cylindrical 3He cell as large as a diameter of 5cm and a length of 10cm can fit. A neutron beam test was performed at the NOP beamline of JRR-3 to see the performance of the NSF. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]