Hirotoshi Hayashida

A study of resolution function on a MIEZE spectrometer

We have installed a MIEZE (modulated intensity by zero effort) spectrometer in the C3-1-2-2(MINE1) port at JRR-3M. In the MIEZE spectrometer, a sample is placed after the analyzer. Thus the contrast of the MIEZE signal can be observed without reduction even in the case of magnetic scattering where the signal for NSE (neutron spin echo) and NRSE (neutron resonance spin echo) instruments is less than half. The MIEZE signal is sensitive to the dispersion of neutron trajectories from the sample to the detector. In other words, the MIEZE signal is reduced only due to the dispersion even without in- and quasi-elastic scattering. We studied the correlation between experimental configuration and its resolution function using the Monte Carlo simulation. We prepared a magnetite ferrofluid sample with a typical particle diameter of 84 A, and examined the simulation model by experiments.

Improvement of 3 He Nuclear Polarization for Neutron Scattering

Nuclear-polarized 3 He gas has recently been widely used in neutron facilities around the world for polarized neutron scattering. The large neutron absorption cross-section of 3 He depends strongly on the 3 He-spin and the neutron-spin directions, and a polarized neutron beam can be easily obtained by passing the beam through polarized 3 He gas, thus constituting a neutron spin filter (NSF). The relationships between neutron polarization Pn, neutron transmission Tn, and 3 He polarization PHe are:

Development of AC Magnetic Field Imaging Technique Using Polarized Pulsed Neutrons at J-PARC

We have been developing a quantitative magnetic field imaging technique at J-PARC. As was previously reported [1], we successfully quantified strength and direction of a static magnetic field by analyzing the wavelength dependence of polarization position by position for images, which were obtained using a time-of-flight (TOF) method of pulsed neutrons. Applying this method to observe a magnetic field in industrial products, such as voltage converters and motors, it is necessary to extend this technique to the AC magnetic field driving at a frequency of commercial power supply (50~60Hz). In this study, we attempted to measure an AC magnetic field quantitatively with the TOF method. Magnetic field imaging experiments were performed at the beam line of BL10 “NOBORU” in the Materials and Life science experimental Facility (MLF) of J-PARC. The experimental setup was the same as the previous experiment [1]. An AC magnetic field was produced by applying an AC electric current to a small solenoid coil with the diameter of 5 mm and length of about 50 mm. The frequency of applied field was set to 50.5 Hz, which is slightly higher than that of a two-fold repetition of the pulsed neutrons of J-PARC. Polarization images were obtained under applying the AC field in the coil and wavelength dependence of polarization in a selected area was analyzed, in which polarization changes due to the neutron spin rotation were observed. By fitting the results with a model assuming that only the magnetic field inside the coil contributed to the neutron spin rotation, the amplitude of applied AC field was estimated to be 3.22±0.14×10 A/m, which was corresponded to the designed value of 3.3×10 A/m. This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.