Yoshifumi Sakaguchi

A compact SEOP 3He neutron spin filter with AFP NMR

We developed AFP NMR in an aluminum container for polarized noble gas nuclei. The radio frequency magnetic field inside the aluminum container was designed from computer simulations. The polarization loss by the AFP spin flip of 3He was measured to be as low as 3.8×10−4. With this technique, a compact in-situ polarizing 3He neutron spin filter with AFP NMR is demonstrated.

Development and demonstration of in-situ SEOP 3He spin filter system for neutron spin analyzer on the SHARAKU polarized neutron reflectometer at J-PARC

A new neutron reflectometer, SHARAKU, with a vertical sample-plane geometry was installed at beam line 17 at J-PARC Materials and Life Science Facility. Although a polarizing supermirror was previously installed as a neutron spin analyzer on SHARAKU, a 3He spin filter is advantageous because it can cover a large solid angle. An in-situ SEOP 3He spin filter system using a new compact laser unit has been developed for the analyzer. In this paper, we report a successful off-specular measurement with the new compact in-situ SEOP analyzer at SHARAKU.

Developments of In-Situ SEOP Polarized 3He Neutron Spin Filter in Japan

We launched the polarized 3He neutron spin filters (NSF) project in order to provide neutron polarization for the pulsed neutron beams in Japan. We adopted the in-situ spin exchange optical pumping (SEOP) technique to polarize the nuclear spin of 3He atoms because it has some advantages for our applications. The overall system size is compact and it avoids the problem of the time decay of nuclear spin of 3He thus suppressing the costs of maintenance and providing other advantages [1, 2] with respect to data analysis and quality. In this paper, we performed pulsed neutron beam tests of our compact in-situ SEOP NSF system at the BL10 beamline in the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex (J-PARC). The polarization of the 3He gas reached was 73 % and a pump-up time constant of 9.5 h was observed. This paper is a status report about the development of in-situ SEOP NSF system for the pulsed beam at J-PARC.

Basic Concepts of Polarisation Analysis for Neutron Chopper Spectrometer POLANO at J-PARC

The basic concept underlying the use of neutron polarisers and analysers in a polarised neutron spectrometer which will be constructed in J-PARC/MLF is discussed. The spectrometer, named POLANO, is a compact chopper spectrometer for polarisation analysis in the energy region up to Ei ~200 meV. In the first stage of this project, a 3He spin filter polarised by the spin exchange optical pumping method will be used as the polariser. Based on the optimisations of the filter parameters, we confirm that the designed optimised 3He spin filters will be feasible for use up to 80 meV.

Measurement of Transient Photo-Induced Changes in Thin Films at J-PARC — Time-Resolved Neutron Reflectivity Measurements of Silver Photo-Diffusion into Ge-Chalcogenide Films

Study on photo-induced changes for specific light-sensitive materials is fascinating from both academic and application points of view because it is one of the frontiers in materials science including concepts of electron-excitation and non-equilibrium state, and the materials can be controlled spatially by illuminated area from distant place [1]. With the aid of significant development of light source equipment such as femtosecond ultra-short pulsed laser systems, attractive photo-induced phenomena have been found in many materials in these days. In the leading-edge field, it is quite natural to be interested in finding the structural origin of the photo-induced changes. Although neutron scattering technique has always a difficulty in beam intensity, it is highly expected to be utilized in structural determination for magnetic materials, hydrogenated materials, and X-ray sensitive materials. At the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), the proton beam intensity is now 300kW, and it is planned to go to 1MW in

Development of portable polarized 3He neutron spin filter and its application to magnetic field imaging at J-PARC

In order to expand the measurable neutron energy range up to the energy of epithermal neutrons in polarized neutron experiments, a portable polarized 3He neutron spin filter (NSF) was developed in the Materials and Life science experimental Facility (MLF) at J- PARC. After the generation of 3He polarization through a spin exchange optical pumping method, the NSF was used as a neutron spin polarizer and flipper in a beam line. We constructed a simple neutron spin analysis apparatus with two 3He NSFs and made a preliminary attempt to visualize magnetic fields generated by a coil. The results represented that our apparatus could function for neutron wavelengths between approximately 0.5-5 A through the use of a neutron time-of-flight method.

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 polarized Xe gas target for neutron experiment at J-PARC

At the Materials and Life science experimental Facility (MLF) in J-PARC, an experiment of detecting a neutron polarizing ability caused by a neutron-nuclear spin correlation at a resonant peak of 129Xe is planned. We evaluated measurable quantities based on a neutron optical theorem, developed a polarized Xe gas system, and carried out a feasibility test of our apparatus.

Applications of 3He neutron spin filters on the small-angle neutron scattering spectrometer SANS-J-II

A polarized 3He neutron spin filter has been applied to polarization analysis on the small-angle neutron scattering spectrometer SANS-J-II at JRR-3. Measurements were taken on silver behenate, which has several coherent peaks in the small-angle region with a background of spin incoherent hydrogen scattering. Here we demonstrate that the coherent and spin incoherent scattering were successfully separated by the polarization analysis using the 3He spin filter on the instrument.

Structure of glasses for 3He neutron spin filter cells

In spin-exchange optical pumping, there is unknown excess relaxation, called the X-factor, that limits attainable 3He polarization. It is known that the X-factor depends on the glass containers. Hence, it is expected that there are cell-to-cell variations in microscopic structure among the cells and that these variations affect the attainable 3He polarization. However, microscopic structure of the glasses for 3He neutron spin filters has not been clarified yet. In this paper, we have performed precise X-ray diffraction measurements for the glasses at SPring-8 using synchrotron radiation. The structural differences are observed between several types of glasses, and also, between the GE180 glass pieces with different thermal treatment. Based on the results, the structural influence on the performance of 3He neutron spin filters is discussed.