Local structure analysis of BiNaTiO

Yoneda, Yasuhiro; Nagata, Hajime*; Takenaka, Tadashi*

Journal of the Korean Physical Society, 66(9), p.1339 - 1343, 2015/05

https://doi.org/10.3938/jkps.66.1339

The potential lead-free piezoelectric material bismuth sodium titanate, BiNaTiO (BNT), was investigated by means of high-energy synchrotron X-ray diffraction. BNT has been assumed thus far to exhibit the rhombohedral space group at room temperature. Recently, the average structure of BNT was described by the monoclinic space group . We performed local structure analysis of BNT using atomic pair-distribution function method. The ground state of BNT was found to be rhombohedral structure in which bismuth and sodium atoms were chemically ordered in the perovskite -site.

Design and delivery of beam monitors for the energy-upgraded linac in J-PARC

Miura, Akihiko; Ouchi, Nobuo; Oguri, Hidetomo; Hasegawa, Kazuo; Miyao, Tomoaki*; Ikegami, Masanori*

Journal of the Korean Physical Society, 66(3), p.364 - 372, 2015/02

https://doi.org/10.3938/jkps.66.364

In J-PARC Linac, an energy upgrade project has started to achieve the design beam power of 1 MW at the exit of downstream synchrotron. To meet with significant upgrades of the beam parameters, beam monitors used for the beam commissioning are modified and fabricated. We discuss how to design and assemble the beam monitors for the upgraded Linac. We delivered them for the new upgraded beam line periodically and newly fabricated monitors for the longitudinal matching are also delivered because of the frequency jump between original RF cavity and newly developed cavity. Finally we suppose the commissioning plans to support the monitor check.

Feasibility studies of a vibration wire monitor and a halo scraper in the J-PARC L3BT

Okabe, Kota; Yamamoto, Kazami; Yoshimoto, Masahiro; Kinsho, Michikazu

Journal of the Korean Physical Society, 63(7), p.1379 - 1384, 2013/10

https://doi.org/10.3938/jkps.63.1379

In the J-PARC 3-GeV Rapid Cycle Synchrotron (RCS), transverse beam halo diagnostic and scraping are required to increase the output beam power. Wire scanners and halo scrapers were used for measurement of projected beam distributions to determine the extent of beam halo formation at Linac-3GeV Beam Transport line (L3BT). In order to determine more detail of halo formation, Vibration Wire Monitor (VWM) was installed in L3BT for the beam halo measurement. The high sensitivity of the VWM makes it a prospective one for investigation of beam halo and weak beam scanning. In this paper, we will report a preliminary result of beam halo measurement by VWM and halo scraper at L3BT, and discuss about potential of the VWM for beam halo diagnostic.

Recovery from the earthquake and operation of the J-PARC linac

Ito, Takashi

Journal of the Korean Physical Society, 63(7), p.1243 - 1248, 2013/10

https://doi.org/10.3938/jkps.63.1243

The Japan Proton Accelerator Research Complex (J-PARC) facilities were extensively damaged by the March 2011 earthquake. At the linac facility, a large amount of groundwater leaked into the tunnel. Therefore, the accelerator components were exposed to high-humidity air for several weeks. Vacuum leaks occurred in ion source, MEBT1 and SDTL sections by destruction of vacuum port, beam monitors and bellows. An alignment of the linac was also damaged. There had been observed about 0.2 mm misalignment of the DT bore center in the DTL and the displacement more than 40 mm of the alignment of the cavity. After recovery efforts, we resumed the beam operation in December 2011 and user operation in January 2012. The beam power from the linac reached at 13.3 kW in March 2012, which is the same power as just before the earthquake. In this report, we will present the recovery works from the earthquake and the present operating status of the J-PARC linac.

Si-NMR study of antiferromagnet CeRhSi using single crystals

Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Matsumoto, Yuji; Matsuda, Tatsuma; Haga, Yoshinori

Journal of the Korean Physical Society, 63(3), p.352 - 355, 2013/08

https://doi.org/10.3938/jkps.63.352

Si-NMR Study of antiferromagnet CeRhSi with a tetragonal ThCrSi-type structure has been performed using single crystals. The Knight shifts along the and axes have been measured as a function of temperatures in the paramagnetic state. At ambient pressure, the Knight shifts show the Ising-type anisotropy along the axis, which is similar to the magnetic susceptibility. The hyperfine coupling constants for Si along the and axes have been determined from Knight shifts versus static susceptibility plots.

Powder neutron diffraction study of HoCoGa

Kobayashi, Riki; Kaneko, Koji; Wakimoto, Shuichi; Chi, S.*; Sanada, Naoyuki*; Watanuki, Ryuta*; Suzuki, Kazuya*

Journal of the Korean Physical Society, 63(3), p.337 - 340, 2013/08

https://doi.org/10.3938/jkps.63.337

Shubnikov-de Haas oscillation in PuIn

Haga, Yoshinori; Bauer, E. D.*; Tobash, P. H.*; Mitchell, J. N.*; Ayala-Valenzuela, O.*; McDonald, R. D.*; Mielke, C. H.*; Fisk, Z.

Journal of the Korean Physical Society, 63(3), p.380 - 382, 2013/08

https://doi.org/10.3938/jkps.63.380

Optical conductivity of antiferromagnetic metallic chromium; Mean-field calculation for the multi-orbital Hubbard model

Sugimoto, Kodai*; Toyama, Takami*; Kaneshita, Eiji*; Tsutsui, Kenji

Journal of the Korean Physical Society, 63(3), p.632 - 635, 2013/08

https://doi.org/10.3938/jkps.63.632

Cr is the representative material of multi-orbital antiferromagnetism. We numerically calculate the band structure and density of states in commensurate antiferromagnetic Cr by multi-orbital Hubbard model with mean-field approximation. The result is adopted to the calculation of optical conductivity. The spectra of the optical conductivity is consistent with experimental data, and this promises the validity of our model.

Heavy fermion superconductivity; 5f vs 4f

Fisk, Z.; Haga, Yoshinori

Journal of the Korean Physical Society, 63(3), p.795 - 799, 2013/08

https://doi.org/10.3938/jkps.63.795

Real-time analysis of the spinmotive force due to domain wall motion

Ieda, Junichi; Maekawa, Sadamichi; Yamane, Yuta

Journal of the Korean Physical Society, 62(12), p.1802 - 1806, 2013/06

https://doi.org/10.3938/jkps.62.1802

Spinmotive force, which is induced by motion of a nonuniform magnetic nanostructure, reflects real time dynamics of the magnetization texture. Using numerical simulations we study the spinmotive force associated with domain wall motion and find that its dc component scales with an applied magnetic field even in a field range where the wall motion is no longer associated with periodic angular rotation of the wall magnetization. As the field is increased, spikes in the voltage signals start to appear, which are mainly associated with vortex core nucleation and annihilation. At high fields, the slope of the generated dc voltage with the applied field is expected to be only dependent on the spin polarization of conduction electrons and thus can be used to accurately determine the degree of spin polarization in various materials.