Band gap opening in graphene by hybridization with Au (001) reconstructed surfaces

Terasawa, Tomoo; Matsunaga, Kazuya*; Hayashi, Naoki*; Ito, Takahiro*; Tanaka, Shinichiro*; Yasuda, Satoshi; Asaoka, Hidehito

Physical Review Materials (Internet), 7(1), p.014002_1 - 014002_10, 2023/01

https://doi.org/10.1103/PhysRevMaterials.7.014002

Au(001) surfaces exhibit a complex reconstructed structure [Hex-Au(001)] comprising a hexagonal surface and square bulk lattices, yielding a quasi-one-dimensional corrugated surface. When graphene was grown on this surface, the periodicity of the corrugated surface was predicted to change the electronic structure of graphene, forming bandgaps and new Dirac points. Furthermore, the graphene-Au interface is promising for bandgap generation and spin injection due to band hybridization. Here, we report the angle-resolved photoemission spectroscopy and density functional calculation of graphene on a Hex-Au(001) surface. The crossing point of the original and replica graphene bands showed no bandgap, suggesting that the one-dimensional potential was too small to modify the electronic structure. A bandgap of 0.2 eV was observed at the crossing point of the graphene and Au bands, indicating that the bandgap is generated using hybridization of the graphene and Au bands. We discussed the hybridization mechanism and concluded that the R30 configuration between graphene and Au and an isolated electronic structure of Au are essential for effective hybridization between graphene and Au. We anticipate that hybridization between graphene and Au would result in spin injection into graphene.

Beam-based compensation of extracted-beam displacement caused by field ringing of pulsed kicker magnets in the 3 GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Harada, Hiroyuki; Saha, P. K.; Tamura, Fumihiko; Meigo, Shinichiro; Hotchi, Hideaki; Hayashi, Naoki; Kinsho, Michikazu; Hasegawa, Kazuo

Progress of Theoretical and Experimental Physics (Internet), 2017(9), p.093G01_1 - 093G01_16, 2017/09

AA2017-0286.pdf:4.64MB

https://doi.org/10.1093/ptep/ptx125

The 3 GeV rapid cycling synchrotron (RCS) of the J-PARC is a high intensity proton accelerator of 1 MW. The accelerated proton beams in the RCS are extracted by eight pulsed kicker magnets and are delivered to a materials and life science experimental facility and main ring synchrotron. However, the fields of the magnets experience ringing that displaces the position of the extracted beam. This is a major issue from the viewpoint of target integrity and large beam loss. The ringing was directly measured as the displacement of the extracted beams by using a shorter pulsed beam and scanning the entire trigger timing of the kickers. We managed to cancel out the ringing by optimizing trigger timing and achieved the beam extraction with high accuracy. We developed automatic correction system of the timing and now have a higher stability. In this paper, we report our procedure and experimental results for ringing compensation.

Comparison between Monte Carlo simulation and measurement with a 3D polymer gel dosimeter for dose distributions in biological samples

Furuta, Takuya; Maeyama, Takuya*; Ishikawa, Kenichi*; Fukunishi, Nobuhisa*; Fukasaku, Kazuaki*; Takagi, Shu*; Noda, Shigeho*; Himeno, Ryutaro*; Hayashi, Shinichiro*

Physics in Medicine & Biology, 60(16), p.6531 - 6546, 2015/08

https://doi.org/10.1088/0031-9155/60/16/6531

Low reproducibility of dose distribution in inhomogeneous regions such as soft matter near bones is known with the simple dose analysis currently adopted in treatment planning of particle cancer therapy. Therefore a treatment planning system based on Monte Carlo simulation having better accuracy is highly desired. In order to assess the simulation accuracy of a Monte Carlo simulation code in situations closely related to medical application, we performed a comparison of dose distribution in a biological sample obtained by experiment and that by simulation. In particular, we irradiate a carbon beam on a biological sample composed of fresh chicken meat and bones, with a PAGAT gel dosimeter placed behind it, and compare the complex dose distribution in the gel dosimeter created by the beam passing through the inhomogeneous sample. Monte Carlo simulation using PHITS code was conducted by reconstructing the biological sample from its computed tomography images. The simulation accurately reproduced the experimental distal edge structure of the dose distribution with an accuracy under about 2 mm.

Development of the beam halo monitor in the J-PARC 3-GeV RCS

Yoshimoto, Masahiro; Yamamoto, Kazami; Saha, P. K.; Meigo, Shinichiro; Hotchi, Hideaki; Hayashi, Naoki; Okabe, Kota; Kinsho, Michikazu

Proceedings of 3rd International Particle Accelerator Conference (IPAC '12) (Internet), p.2122 - 2124, 2012/05

http://accelconf.web.cern.ch/accelconf/IPAC2012/papers/moppd073.pdf

Transverse beam halo is one of the most important beam parameters due to limit the performance of the high intensity beam accelerator. Therefore the transverse beam halo measurement is required to increase the beam power of the J-PARC 3-GeV RCS. In order to measure the transverse beam halo during the beam operation, halo monitors which are horizontal and vertical scanning aluminum plates type has been installed in the extraction beam line. But the residual secondary electrons hindered the beam halo diagnostic. We report how to take measures against the intrinsic issues of this monitor.

Study on immobilization technology of radioactive krypton gas by ion-implantation and sputtering process

Samoto, Hirotaka; Kimura, Norimichi; Otani, Takehisa; Sugai, Eiji; Hayashi, Shinichiro

Proceedings of International Conference on Advanced Nuclear Fuel Cycle; Sustainable Options & Industrial Perspectives (Global 2009) (CD-ROM), p.458 - 463, 2009/09

JAEA has been developing technology to immobilize radioactive krypton gas to metal alloy by ion-implantation method as a stable storage technique of krypton gas recovered from a reprocessing plant. The characteristics of implantation of krypton gas and of krypton implanted alloy were investigated by the cold test performed so far. In this paper, we report the results of the hot immobilization test performed at the Krypton Recovery development Facility (hereafter called KRF) which is attached to the Tokai Reprocessing Plant (hereafter called TRP). In this test, we immobilized the radioactive krypton gas recovered from TRP by cryogenic distillation process of KRF and investigated the gas retention characteristics of the implanted alloy.

Criticality safety evaluation in Tokai reprocessing plant

Shirai, Nobutoshi; ; ; Shirozu, Hidetomo; Sudo, Toshiyuki; Hayashi, Shinichiro;

JNC TN8410 2000-006, 116 Pages, 2000/04

JNC-TN8410-2000-006.pdf:2.77MB

Criticality limits for equipments in Tokai Reprocessing Plant which handle fissile material solution and are under shape and dimension control were reevaluated based on the guideline No.10 "Criticality safety of single unit" in the regulatory guide for reprocessing plant safety. This report presents criticality safety evaluation of each equipment as single unit. Criticality safety of multiple units in a cell or a room was also evaluated. The evaluated equipments were ones in dissolution, separation, purification, denitration, Pu product storage, and Pu conversion processes. As a result, it was reconfirmed that the equipments were safe enough from a view point of criticality safety of single unit and multiple units.

None

; ; ; Hayashi, Shinichiro; ;

PNC TN8410 96-055, 147 Pages, 1998/02

PNC-TN8410-96-055.pdf:4.96MB

None

Study on immobilization technology of krypton gas by ion-implantation and sputtering process

Hayashi, Shinichiro; ; ;

Proceedings of International Conference on Future Nuclear Systems (GLOBAL'97), p.620 - 625, 1997/00

None

Three decades of forward steps and prospect in Tokai reprocessing plant, 3; Operation experience and improvement on the dissolution process and clarification process

Suzuki, Kazuyuki; Kikuchi, Hideki; Hata, Katsuro; Tanaka, Ken; Miyamoto, Masanori; Nakamura, Yoshinobu; Hayashi, Shinichiro

no journal, , 

no abstracts in English

Corrosion evaluation of the dissolver

Suzuki, Kazuyuki; Nakamura, Yoshinobu; Hikita, Keiichi; Kogawa, Takayuki; Hayashi, Shinichiro

no journal, , 

The reprocessing plant dissolves Spent Fuels and it is a process to attract U and Pu after the removal of the Fission Products. Because dissolver is a tank with boiling nitric acid, there is it in the severe corrosion environment. Corrosion environment of the heat transfer surface is the severest. Therefore, the dissolver is made in High Chrome Nickel Steel in consideration of corrosion resistance. This paper reports a supersonic wave measurement method and corrosion rate of the dissolver.