Challenge to charge exchange with pure carbon foil in the J-PARC 3GeV synchrotron

Nakanoya, Takamitsu; Yoshimoto, Masahiro; Saha, P. K.; Takeda, Osamu*; Saeki, Riuji*; Muto, Masayoshi*

Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.937 - 941, 2023/11

https://www.pasj.jp/web_publish/pasj2023/proceedings/PDF/FRP3/FRP38.pdf

In the J-PARC 3GeV Rapid Cycling Synchrotron (RCS), the 400MeV H beam is changed to H+ beam by a charge exchange foil and accelerated to 3GeV. So far, RCS had used two types of charge exchange foil. One is the HBC (Hybrid Boron mixed Carbon) foil and the other is the Kaneka GTF (Graphene Thin Film). HBC foil is a patented deposition method developed at KEK for the stable production of thick carbon foil. Initially, the RCS used HBC foil produced atKEK. However, in 2017, JAEA had started HBC foil production and has been using it since then. Recently, we have succeeded in depositing thick pure carbon foil, which had been considered difficult to produce by the arc deposition method. As a new challenge, this pure carbon foil was used in the user operation from March 2023. As a result, Pure carbon foils showed less deformation and more stable charge exchange performance than HBC and GTF.

Remnants of the nonrelativistic Casimir effect on the lattice

Nakayama, Katsumasa*; Suzuki, Kei

Physical Review Research (Internet), 5(2), p.L022054_1 - L022054_6, 2023/06

https://doi.org/10.1103/PhysRevResearch.5.L022054

The Casimir effect is a fundamental quantum phenomenon induced by the zero-point energy for a quantum field. It is well-known for relativistic fields with a linear dispersion relation, while its existence or absence for nonrelativistic fields with a quadratic dispersion is an unsettled question. Here, we investigate the Casimir effects for various dispersion relations on the lattice. We find that Casimir effects for dispersions proportional to an even power of momentum are absent in a long distance under some types of boundary conditions, while a remnant of the Casimir effect survives in a short distance. The concepts of such absence and remnants of Casimir effect help us to understand observables in finite-size materials with quantum fields on the lattice, such as thin films, narrow nanoribbons, and short nanowires. In terms of this effect, we also give a reinterpretation of the Casimir effect for massive fields.

Crystal structure, photomagnetic and dielectric properties of a cyanido-bridged Cu-Mo assembly film

Ikeda, Yusuke*; Matsumura, Daiju; Tsuji, Takuya; Namai, Asuka*; Imoto, Kenta*; Tokoro, Hiroko*; Nakabayashi, Koji*; Okoshi, Shinichi*

Inorganica Chimica Acta, 550, p.121434_1 - 121434_8, 2023/03

https://doi.org/10.1016/j.ica.2023.121434

Modulation of Dirac electrons in epitaxial BiSe ultrathin films on van der Waals ferromagnet CrSiTe

Kato, Takemi*; Sugawara, Katsuaki*; Ito, Naohiro*; Yamauchi, Kunihiko*; Sato, Takumi*; Oguchi, Tamio*; Takahashi, Takashi*; Shiomi, Yuki*; Saito, Eiji; Sato, Takafumi*

Physical Review Materials (Internet), 4(8), p.084202_1 - 084202_6, 2020/08

https://doi.org/10.1103/PhysRevMaterials.4.084202

Fabrication status of charge stripper foil for 3 GeV synchrotron of J-PARC

Nakanoya, Takamitsu; Yoshimoto, Masahiro; Yamazaki, Yoshio; Takeda, Osamu*; Saeki, Riuji*; Muto, Masayoshi*

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.545 - 549, 2019/07

In the 3 GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research complex (J-PARC), we adopted the carbon stripper foil for the multi-turn H- charge exchange injection. The charge exchange foil which use in RCS is fabricated by the arc discharge method with the boron doped carbon electrode. The foil fabricated this method is called HBC foil (Hybrid Boron mixed Carbon stripper foil). HBC foil had been developed at KEK. It has high durability for the beam irradiation damage. In past days, the foil fabrication process was conducted in KEK Tsukuba-site and the foil preparation process was conducted in JAEA Tokai-site. In 2017, the foil deposition apparatus has been relocated from KEK to JAEA, and we started both processes in Tokai-site. We carried out the offline beam irradiation test for the new HBC foil which fabricated in JAEA, and we confirmed that its performance is equivalent to the original HBC foil. Next we tested a new HBC foil with actual beam in RCS and we confirmed it could withstand 1 week beam irradiation. After that, we started user operation with the new HBC foil in 2018. So far we accomplished stable user operation for one year by using the new HBC foil only.

Micro-orientation control of silicon polymer thin films on graphite surfaces modified by heteroatom doping

Shimoyama, Iwao; Baba, Yuji; Hirao, Norie*

Advances in Engineering (Internet), 1 Pages, 2018/02

The performance of organic devices largely depends on molecular orientation in organic films. Whereas micro-orientation control of organic molecules is an indispensable technology for integration of organic devices, the method has not been established. We attempted to control micro-orientation of polydimethylsilane (PDMS) thin films by deposition of PDMS on graphite substrates modified by hetero atom doping using ion beam. Polarization dependence measurements of X-ray absorption spectroscopy and molecular orbital calculations clarified that PDMS films have lying, standing, and random orientations on the non irradiated, N-irradiated, and Ar-irradiated graphite surfaces, respectively. Furthermore, photoemission microscopy observation clarified that a PDMS film showed micro-patterns on a graphite surface with a microstructure on the order of m by separating N-irradiated and non irradiated areas. These results demonstrate our method is promising for micro-orientation of organic molecules.

Micro-orientation control of silicon polymer thin films on graphite surfaces modified by heteroatom doping

Shimoyama, Iwao; Baba, Yuji; Hirao, Norie*

Applied Surface Science, 405, p.255 - 266, 2017/05

https://doi.org/10.1016/j.apsusc.2017.01.297

NEXAFS spectroscopy is applied to study orientation structures of polydimethylsilane (PDMS) films deposited on heteroatom-doped graphite substrates prepared by ion beam doping. The Si -edge NEXAFS spectra of PDMS show opposite trends of polarization dependence for non irradiated and N-irradiated substrates, and show no polarization dependence for an Ar-irradiated substrate. Based on a theoretical interpretation of the NEXAFS spectra via first-principles calculations, we clarify that PDMS films have lying, standing, and random orientations on the non irradiated, N-irradiated, and Ar-irradiated substrates, respectively. Furthermore, photoemission electron microscopy indicates that the orientation of a PDMS film can be controlled with microstructures on the order of m by separating irradiated and non irradiated areas on the graphite surface. These results suggest that surface modification of graphite using ion beam doping is useful for micro-orientation control of organic thin films.

Growth of single-phase nanostructured ErO thin films on Si (100) by ion beam sputter deposition

Mao, W.*; Fujita, Masaya*; Chikada, Takumi*; Yamaguchi, Kenji; Suzuki, Akihiro*; Terai, Takayuki*; Matsuzaki, Hiroyuki*

Surface & Coatings Technology, 283, p.241 - 246, 2015/12

https://doi.org/10.1016/j.surfcoat.2015.10.060

Single-phase nanocrystalline thin films of ErO (440) has been first prepared using Si (100) substrates by ion beam sputter deposition at 973 K at a pressure of 10 Pa and - annealing at 1023 K at a pressure of 10 Pa. Er silicides formed during the deposition are eliminated via the annealing, which results in the single phase and the smooth surface of the ErO thin films. The epitaxial relationship between Si (100) and ErO (110) is clarified by X-ray diffraction and reflection high energy electron diffraction.

Depth analysis of the surface of MgSi crystals with XAS and XPS

Yamamoto, Hiroyuki; Nojima, Takehiro; Esaka, Fumitaka

Photon Factory Activity Report 2014, Part B, P. 112, 2015/00

http://pfwww.kek.jp/acr/2014pdf/part_b/pf14b0112.pdf

In order to develop silicon-based electronic devices, metal silicides are widely studied. Information of the surface chemical states of metal silicides is important to obtain homo-epitaxial films with excellent quality. In this work, depth analysis of surface chemical states of MgSi crystals is carried by XPS. Depth analysis is also performed in XAS measurement with a partial electron yield (PEY) mode. The Si 1s XPS spectra of the cleaved surface of the MgSi crystal indicates that SiO is formed on the surface of the MgSi crystal. Here, no peak assigned to SiO structure is observed. The Si K-edge XAS spectra obtained with the PEY mode show a peak at 1843.7 eV, which can be assigned to SiO structure.

Molecular orientation of pentacene derivative

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Photon Factory Activity Report 2013, Part B, P. 518, 2014/00

Organic electrically conducting -stacked small molecules are widely regarded as promising materials for future application of low-cost and flexible nanoelectronics. Pentacene is one of the most promising organic semiconductors because of its excellent device performance. Direct measurements of electronic structures of unoccupied states of organic semiconductors lead to better understanding of mechanism of electron conduction. For probing unoccupied partial density of states (DOS), X-ray absorption spectroscopy (XAS) is commonly used, where selective excitation of the 1s core electron to the unoccupied conduction band is possible. The molecular orientation of pentacene derivative has been investigated by angle dependent XAS measurements. Electronic states were calculated by DVX method.