Roles of excess minority carrier recombination and chemisorbed O species at SiO/Si interfaces in Si dry oxidation; Comparison between p-Si(001) and n-Si(001) surfaces

Tsuda, Yasutaka; Yoshigoe, Akitaka; Ogawa, Shuichi*; Sakamoto, Tetsuya*; Yamamoto, Yoshiki*; Yamamoto, Yukio*; Takakuwa, Yuji*

Journal of Chemical Physics, 157(23), p.234705_1 - 234705_21, 2022/12

https://doi.org/10.1063/5.0109558

High reactivity of HO vapor on GaN surfaces

Sumiya, Masatomo*; Sumita, Masato*; Tsuda, Yasutaka; Sakamoto, Tetsuya; Sang, L.*; Harada, Yoshitomo*; Yoshigoe, Akitaka

Science and Technology of Advanced Materials, 23(1), p.189 - 198, 2022/00

https://doi.org/10.1080/14686996.2022.2052180

GaN is an attracting material for power-electronic devices. Understanding the oxidation at GaN surface is important for improving metal-oxide-semiconductor (MOS) devices. In this study, the oxidation at GaN surfaces depending on the GaN crystal planes (+c, -c, and m-plane) was investigated by real time XPS and DFT-MD simulation. We found that HO vapor has the highest reactivity due to the spin interaction between HO and GaN surfaces. The bond length between the Ga and N on the -c GaN surface was increased by OH attacking the back side of three-fold Ga atom. The chemisorption on the m-plane was dominant. The intense reactions of oxidation and AlGaN formation for p-GaN were observed at the interface of the AlO layer deposited by ALD using HO vapor. This study suggests that an oxidant gas other than HO and O should be used to avoid unintentional oxidation during AlGaN atomi layer deposition.

Development of a pulsed neutron three-dimensional imaging system using a highly sensitive image-intensifier at J-PARC

Segawa, Mariko; Oi, Motoki; Kai, Tetsuya; Shinohara, Takenao; Kureta, Masatoshi; Sakamoto, Kensaku; Imaki, Tadashi*

Nuclear Instruments and Methods in Physics Research A, 769, p.97 - 104, 2015/01

https://doi.org/10.1016/j.nima.2014.09.030

First neutron production utilizing J-PARC pulsed spallation neutron source JSNS and neutronic performance demonstrated

Maekawa, Fujio; Harada, Masahide; Oikawa, Kenichi; Teshigawara, Makoto; Kai, Tetsuya; Meigo, Shinichiro; Oi, Motoki; Sakamoto, Shinichi; Takada, Hiroshi; Futakawa, Masatoshi; et al.

Nuclear Instruments and Methods in Physics Research A, 620(2-3), p.159 - 165, 2010/08

https://doi.org/10.1016/j.nima.2010.04.020

The J-PARC 1-MW pulsed spallation neutron source JSNS was successfully launched on 30th of May 2008. To demonstrate the unique features of the moderator design and the neutronic performance of JSNS the neutron spectral intensity, absolute neutron flux, and time structure of the neutron pulse shapes etc have been measured using several neutron instruments since then. The measured energy spectra clearly revealed the feature of the para-hydrogen, as expected when designing the moderator. The measured neutron flux below 0.4 eV agreed with the corresponding design value within 20%, thus suggesting that the JSNS design calculations to have been reliable. World-class high-resolution diffraction data could be recorded due to the suitability of design of the moderators and the instruments. Another world-class high-intensity neutron flux was also capable of being demonstrated due to the unique design of the large cylindrical coupled moderator.

Characterization of electrode/electrolyte interface using X-ray reflectometry and LiNiCoO epitaxial film electrode synthesized by pulsed laser deposition method

Hirayama, Masaaki*; Sakamoto, Kazuyuki*; Hiraide, Tetsuya*; Mori, Daisuke*; Yamada, Atsuo*; Kanno, Ryoji*; Sonoyama, Noriyuki*; Tamura, Kazuhisa; Mizuki, Junichiro

Electrochimica Acta, 53(2), p.871 - 881, 2007/12

https://doi.org/10.1016/j.electacta.2007.07.074

An experimental technique was developed for detecting structure changes at the electrode/electrolyte interface of lithium cell using synchrotron X-ray reflectometry and two-dimensional model electrodes with a restricted lattice plane. The electrode was constructed with an epitaxial film of LiNiCoO synthesized by the pulsed laser deposition method. These films provided an ideal reaction field suitable for detecting structure changes at the electrode/electrolyte interface during the electrochemical reaction. The X-ray reflectometry indicated a formation of a thin-film layer at the LiNiCoO (1 1 0)/electrolyte interface during the first charge-discharge cycle, while the LiNiCoO (0 0 3) surface showed an increase in the surface roughness without forming the surface thin-film layer.

Characteristics of 28 GHz gyrotron for ECRH on GAMMA10

Kamata, Yasuhiro*; Imai, Tsuyoshi*; Tatematsu, Yoshinori*; Watanabe, Osamu*; Minami, Ryutaro*; Saito, Teruo*; Sakamoto, Keishi; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Machida, Norihito*; et al.

Fusion Science and Technology, 51(2T), p.412 - 414, 2007/02

https://doi.org/10.13182/FST07-A1419

no abstracts in English

Development of beam monitor DAQ system for 3NBT at J-PARC

Oi, Motoki; Kai, Tetsuya; Meigo, Shinichiro; Kinoshita, Hidetaka; Sakai, Kenji; Sakamoto, Shinichi; Kaminaga, Masanori; Kato, Takashi; Kato, Tadahiko*

Europhysics Conference Abstracts, 29J, 6 Pages, 2005/00

The 3GeV proton beam transport facility (3NBT) is a high-intensity proton beam line from the 3GeV Rapid Cycling Synchrotron (RCS) to the Material and Life science Facility (MLF) at Japan Proton Accelerator Research Complex (J-PARC). In order to allow hands-on maintenance, a design criterion has been that the average beam loss at 3NBT be less than 1W/m. The systems for beam monitoring and magnet power control play an important role. In J-PARC, the Experimental Physics and Industrial Control System (EPICS) [1] will be used for the main control system. For the proton beam monitor system of 3NBT, EPICS is used and it has to work at 25Hz. In this study, a data acquisition system for the proton beam monitors is presented that has been developed with EPICS. Its performance has been investigated under 25Hz frequency condition.

Development of 972MHz klystron for high-intensity proton accelerator facility

Chishiro, Etsuji; Kobayashi, Tetsuya; Yamazaki, Masayoshi*; Suzuki, Hiroyuki*; Hori, Toshihiko*; Sakamoto, Mitsunori*; Urakata, Hiroto*; Miyake, Setsuo*; Fukuda, Shigeki*; Anami, Shozo*

Proceedings of 21st International Linac Conference, p.455 - 457, 2003/00

In the lilac of the High-Intensity Proton Accelerator Facility, 972MHz klystrons are adopted as the RF source for the acceleration from 190MeV to 400MeV. The klystron is required the RF power of 2.5 MW to drive the ACS accelerator. A prototype klystron was produced, and was evaluated the RF characteristics at the test stand in the JAERI. At the first test, a saturation power of 2.1 MW was obtain on the cathode voltage of 104kV, and an unstable output power causing by a gun oscillation was observed.

Simulation of the background for detection system in the indoor environments of concrete buildings

Tsutsumi, Masahiro; Oishi, Tetsuya; Kinouchi, Nobuyuki; Sakamoto, Ryuichi; Yoshida, Makoto

Journal of Nuclear Science and Technology, 38(12), p.1109 - 1114, 2001/12

https://doi.org/10.3327/jnst.38.1109

In order to predict the indoor background spectra to gamma detection systems, the gamma radiation field in a concrete building is studied by the Monte Carlo simulations. The parameters of wall thickness, room shape and dimensions were considered in the modeling. The indoor source geometry was simulated by a spherical layer model with the intention of easy and effective calculations. The model was applied to an unshielded germanium detector and the detection system with a more complex shielding configuration. As the results, we found that the indoor radiation field in concrete buildings can be predicted well with the source geometry of a spherical concrete layer of 25cm thickness and with the source of the natural major three components of the U series, Th series and K that are homogeneously distributed. The simulation model is useful for designing and optimizing gamma detection systems or shielding assemblies.

Beam transport to the proton beam dump at J-PARC 3GeV proton transport facility

Oi, Motoki; Kai, Tetsuya; Ono, Takehiro; Ikezaki, Kiyomi; Haraguchi, Tetsuya; Fujimori, Hiroshi*; Sakamoto, Shinichi; Meigo, Shinichiro

no journal, , 

no abstracts in English