Current numbers of qubits and their uses

Ichikawa, Tsubasa*; Hakoshima, Hideaki*; Inui, Koji*; Ito, Kosuke*; Matsuda, Ryo*; Mitarai, Kosuke*; Miyamoto, Koichi*; Mizukami, Wataru*; Mizuta, Kaoru*; Mori, Toshio*; et al.

Nature Reviews Physics (Internet), 6(6), p.345 - 347, 2024/06

https://doi.org/10.1038/s42254-024-00725-0

One-dimensional band structure in quasi-two-dimensional -MoO revealed by angle-resolved photoelectron spectroscopy and first-principles calculation

Sumida, Kazuki; Higaki, Sota*; Sato, Hitoshi*; Tsuru, Daichi*; Miyamoto, Koji*; Okuda, Taichi*; Kuroiwa, Yoshihiro*; Moriyoshi, Chikako*; Takase, Koichi*; Oguchi, Tamio*; et al.

Journal of the Physical Society of Japan, 92(8), p.084706_1 - 084706_6, 2023/08

https://doi.org/10.7566/JPSJ.92.084706

Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone

Hirahara, Toru*; Otrokov, M. M.*; Sasaki, Taisuke*; Sumida, Kazuki*; Tomohiro, Yuta*; Kusaka, Shotaro*; Okuyama, Yuma*; Ichinokura, Satoru*; Kobayashi, Masaki*; Takeda, Yukiharu; et al.

Nature Communications (Internet), 11, p.4821_1 - 4821_8, 2020/09

https://doi.org/10.1038/s41467-020-18645-9

Nature of the Dirac gap modulation and surface magnetic interaction in axion antiferromagnetic topological insulator MnBiTe

Shikin, A. M.*; Estyunin, D. A.*; Klimovskikh, I. I.*; Filnov, S. O.*; Kumar, S.*; Schwier, E. F.*; Miyamoto, Koji*; Okuda, Taichi*; Kimura, Akio*; Kuroda, Kenta*; et al.

Scientific Reports (Internet), 10, p.13226_1 - 13226_13, 2020/08

https://doi.org/10.1038/s41598-020-70089-9

Development of the unmanned surface vehicle for radiation monitoring at seabed; Observation of temporal change of radiocesium concentration in the sea bottom sediment at coastal zone of Fukushima

Sanada, Yukihisa; Miyamoto, Kenji*; Ochi, Kotaro; Matsuzaki, Koji*; Ogawa, Toshihiro*; Senga, Yasuhiro*

Kaiyo Riko Gakkai-Shi, 24(2), p.9 - 18, 2018/12

https://doi.org/10.14928/amstec.24.2_9

Seven years passed since Fukushima Dai-ichi Nuclear Power Station accident which was caused large amount of radionuclide release to the sea. Elucidation of behavior mechanism of radiocesium in the seabed is required for restarting fishing industry. We developed radiation detection system using the unmanned surface vehicle for in-situ measurement of radiocesium concentration in seabed sediment. This system is able to automatically navigate to measurement point and obtain the radiation data on the bottom sediment. The detector was calibrated by comparing the actual sediment samples. The periodical measurement off-shore the Fukushima Prefecture was performed using developed this system. As these results, distribution of radiocesium concentration was changed due to oceanographic condition. However, radiocesium inventory was tendency to decrease according to radiocesium half-life in measurement area. This system is effective for elucidation of behavior mechanism of radiocesium because it can easily measure the radiocesium concentration in the bottom sediment.

Measurement of heat load density profile on acceleration grid in MeV-class negative ion accelerator

Hiratsuka, Junichi; Hanada, Masaya; Kojima, Atsushi; Umeda, Naotaka; Kashiwagi, Mieko; Miyamoto, Kenji*; Yoshida, Masafumi; Nishikiori, Ryo; Ichikawa, Masahiro; Watanabe, Kazuhiro; et al.

Review of Scientific Instruments, 87(2), p.02B137_1 - 02B137_3, 2016/02

https://doi.org/10.1063/1.4935636

To understand the physics of the negative ion extraction/acceleration, the heat load density profile on the acceleration grid has been firstly measured in the ITER prototype accelerator where the negative ions are accelerated to 1 MeV with five acceleration stages. In order to clarify the profile, the peripheries around the apertures on the acceleration grid were separated into thermally insulated 34 blocks with thermocouples. The spatial resolution is as low as 3 mm and small enough to measure the tail of the beam profile with a beam diameter of 16 mm. It was found that there were two peaks of heat load density around the aperture. These two peaks were also clarified to be caused by the intercepted negative ions and secondary electrons from detailed investigation by changing the beam optics and gas density profile. This is the first experimental result, which is useful to understand the trajectories of these particles.

Study of negative hydrogen ion beam optics using the 2D PIC method

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya; Kojima, Atsushi

AIP Conference Proceedings 1515, p.22 - 30, 2013/02

https://doi.org/10.1063/1.4792766

We have developed the integrated 2D PIC code for the analysis of the negative ion beam optics, in which an overall region from the source plasma to the accelerator is modeled. Thus, the negative ion trajectory can be solved self-consistently without any assumption of the plasma meniscus form initially. This code can reproduce the negative ion beam halo observed in an actual negative ion beam. It is confirmed that the surface produced negative ions which are extracted near the edge of the meniscus can be one of the reasons for the beam halo: these negative ions are over-focused due to the curvature of the meniscus. The negative ions are not focused by the electrostatic lens, and consequently become the beam halo.

Study of beam optics and beam halo by integrated modeling of negative ion beams from plasma meniscus formation to beam acceleration

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya; Kojima, Atsushi

Applied Physics Letters, 102(2), p.023512_1 - 023512_4, 2013/01

https://doi.org/10.1063/1.4788725

To understand the physical mechanism of the beam halo formation in negative ion beams, a two-dimensional particle-in-cell code for simulating the trajectories of negative ions created via surface production has been developed. The simulation code reproduces a beam halo observed in an actual negative ion beam. The negative ions extracted from the periphery of the plasma meniscus (an electro-static lens in a source plasma) are over-focused in the extractor due to large curvature of the meniscus.

Effects of ELM mitigation coils on energetic particle confinement in ITER steady-state operation

Tani, Keiji*; Shinohara, Koji; Oikawa, Toshihiro*; Tsutsui, Hiroaki*; Miyamoto, Seiji; Kusama, Yoshinori; Sugie, Tatsuo

Nuclear Fusion, 52(1), p.013012_1 - 013012_21, 2012/01

https://doi.org/10.1088/0029-5515/52/1/013012

Simulation of chemical and electrochemical behavior of actinides and fission products in pyrochemical reprocessing

Minato, Kazuo; Hayashi, Hirokazu; Mizuguchi, Koji*; Sato, Takeyuki*; Amano, Osamu*; Miyamoto, Satoshi*

Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), p.778 - 781, 2003/11

The simulation technology for the pyrochemical reprocessing of oxide fuels was developed to analyze experimental data, to predict experimental results, and to propose adequate conditions and processes. The simulation method was based on calculations of chemical equilibrium and electrochemical reactions. Some model calculations to simulate the experimental results were made on the process of electro-codeposition of UO and PuO. Although it was difficult to trace the experiments and compare the calculated results with the experimental results quantitatively due to the limitation of available data on the experimental conditions, the calculated results were consistent with the experimental results. The phenomena of the repeated oxidation-reduction reactions between Pu and Pu ions and those between Fe and Fe ions were theoretically analyzed,which caused the low current efficiency in the electro-codeposition process.