Surface morphology of naphtacene single crystals grown by the physical vapor transport technique

Jo, Sadaharu*; Suzuki, Seiya; Yoshimura, Masamichi*

Japanese Journal of Applied Physics, 63(6), p.065503_1 - 065503_4, 2024/06

https://doi.org/10.35848/1347-4065/ad45d3

In situ transmission electron microscopy observation of melted germanium encapsulated in multilayer graphene

Suzuki, Seiya; Nemoto, Yoshihiro*; Shiiki, Natsumi*; Nakayama, Yoshiko*; Takeguchi, Masaki*

Annalen der Physik, 535(9), p.2300122_1 - 2300122_12, 2023/09

AA2022-1001.pdf:3.25MB

https://doi.org/10.1002/andp.202300122

Microparticles with diverse sizes and morphologies from mechanical and laser cutting of fuel debris simulants and geopolymer as a covering material

Zhou, Q.*; Saito, Takumi*; Suzuki, Seiya; Yano, Kimihiko; Suzuki, Shunichi*

Journal of Nuclear Science and Technology, 58(4), p.461 - 472, 2021/04

https://doi.org/10.1080/00223131.2020.1869623

Year-round variations in the fluvial transport load of particulate Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident

Matsunaga, Takeshi; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi; Tsuzuki, Katsunori; Nishimura, Shusaku; Koarashi, Jun; Otosaka, Shigeyoshi; Sato, Tsutomu*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 310(2), p.679 - 693, 2016/11

AA2015-0821.pdf:3.78MB

https://doi.org/10.1007/s10967-016-4840-3

Particulate Cs in stream water was collected continuously for two years in order to assess the long-term trend of the Cs discharge from the forest environment. Sampling was conducted from December 2011 to December 2013 in a mountainous stream, which received the Cs from the Fukushima Daiichi Nuclear Power Plant accident. A seasonal increase in fluvial transport load of particulate Cs associated with suspended solids (SS) was observed in August and September when rainfall was abundant. The particulate Cs concentration decreased at a faster rate than the rate due to radioactive decay. This decrease might be resulted from redistribution of the easily eroded and polluted soil surface due to heavy rain events such as typhoons. These findings indicate that the particulate Cs load was subject to the inter-annual variations in rainfalls, and decreased gradually over a long period of time due to a decrease in Cs concentration in SS.

Biogeochemical signals from deep microbial life in terrestrial crust

Suzuki, Yohei*; Konno, Yuta*; Fukuda, Akari*; Komatsu, Daisuke*; Hirota, Akinari*; Watanabe, Katsuaki*; Togo, Yoko*; Morikawa, Noritoshi*; Hagiwara, Hiroki; Aosai, Daisuke*; et al.

PLOS ONE (Internet), 9(12), p.e113063_1 - e113063_20, 2014/12

https://doi.org/10.1371/journal.pone.0113063

We present multi-isotopic evidence of microbially mediated sulfate reduction in a granitic aquifer, a representative of the terrestrial crust habitat. Deep groundwater of meteoric origin was collected from underground boreholes drilled into the Cretaceous Toki granite, central Japan. A large sulfur isotopic fractionation of 20-60 permil diagnostic to microbial sulfate reduction is associated with the investigated groundwater containing sulfate below 0.2 mM. In contrast, a small carbon isotopic fractionation ( 30 permil) is not indicative of methanogenesis. Our results demonstrate that the deep biosphere in the terrestrial crust is metabolically active and playing a crucial role in the formation of reducing groundwater even under low energy fluxes.

Development of LLRF control software for the J-PARC 400 MeV Linac

Fang, Z.*; Michizono, Shinichiro*; Anami, Shozo*; Yamaguchi, Seiya*; Naito, Fujio*; Fukui, Yuji*; Kobayashi, Tetsuya; Suzuki, Hiroyuki; Chishiro, Etsuji; Shinozaki, Shinichi

Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.1068 - 1070, 2010/08

http://www.pasj.jp/web_publish/pasj7/proceedings/P_5PM/P_EH_5PM/THPS092.pdf

The output energy of the J-PARC proton Linac will be upgraded from 181 to 400 MeV in the next two years by adding 972-MHz high-beta acceleration sections. The RF signals are controlled by the FPGA-based digital feedback control systems installed in a compact PCI (cPCI). Recently, the LLRF control software has also been upgraded for the J-PARC Linac, especially for the 972-MHz high-beta systems. Many functions have been added to the LLRF control software, such as (1) gradually increasing the feedback gains in the feedback loop instead of fixed ones, (2) automatic chopped-beam compensation, (3) automatically switching the beam loading compensation in accordance with the different beam operation mode, (4) input RF-frequency tuning carried out by a FPGA to match the RF cavities during the RF start-up, (5) auto-tuning of the RF cavity tuner by detecting the phase curve of the RF cavity during the field decay instead of the phase difference between the cavity input and output signals.

Automatic frequency matching for cavity warming-up in J-PARC linac digital LLRF control

Kobayashi, Tetsuya; Anami, Shozo*; Michizono, Shinichiro*; Fang, Z.*; Suzuki, Hiroyuki; Yamaguchi, Seiya*

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1065 - 1067, 2010/03

http://www.pasj.jp/web_publish/pasj6/papers/fpaca47.pdf

In the J-PARC Linac LLRF, for the cavity start-up, the cavity resonance is automatically controlled to be the accelerating frequency (324 MHz and 972 MHz) with a mechanical tuner installed on the cavity. Figure 1: FPGA block diagram of the digital FB and FF control system for the J-PARC linac LLRF. We are planning to introduce a new method of the cavity-input frequency matching into the digital LLRF control system instead of the tuner control for the cavity start-up. In order to match the frequency with the detuned cavity, the output RF frequency is modulated by way of phase rotation with the I/Q modulator, while the cavity tuner is fixed. The detuning of the cavity is obtained from phase gradient of the cavity field decay at the RF-pulse end and the phase rotation is automatically controlled by a FPGA and a DSP. No hardware modification is necessary for this frequency modulation method.

Automatic frequency matching for cavity warming-up in J-PARC linac digital LLRF control

Kobayashi, Tetsuya; Suzuki, Hiroyuki; Anami, Shozo*; Yamaguchi, Seiya*; Michizono, Shinichiro*; Fang, Z.*

Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.2213 - 2215, 2009/05

In the J-PARC Linac LLRF, for the cavity start-up, the cavity resonance is automatically controlled to be the accelerating frequency (324 MHz and 972 MHz) with a mechanical tuner installed on the cavity. We are planning to introduce a new method of the cavity-input frequency matching into the digital LLRF control system instead of the tuner control for the cavity start-up. In order to match the frequency with the detuned cavity, the output RF frequency is modulated by way of phase rotation with the I/Q modulator, while the cavity tuner is fixed. The detuning of the cavity is obtained from phase gradient of the cavity field decay at the RF-pulse end and the phase rotation is automatically controlled by a FPGA and a DSP. No hardware modification is necessary for this frequency modulation method. The cost reduction or the high durability for the mechanical tuner production is expected in the future.

Operating experience of the J-PARC linac

Hasegawa, Kazuo; Asano, Hiroyuki; Chishiro, Etsuji; Hori, Toshihiko; Ito, Takashi; Kobayashi, Tetsuya; Kondo, Yasuhiro; Namekawa, Yuya; Oguri, Hidetomo; Okoshi, Kiyonori; et al.

Proceedings of 24th International Linear Accelerator Conference (LINAC 2008) (CD-ROM), p.55 - 57, 2009/00

http://accelconf.web.cern.ch/accelconf/LINAC08/papers/mop004.pdf

The beam commissioning of the J-PARC linac started in November 2006 and 181 MeV acceleration was successfully achieved in January 2007. The linac has delivered beams to the 3 GeV Rapid Cycling Synchrotron for its commissioning, and then, the subsequent Main Ring Synchrotron and the neutron target commissioning. The linac uses a Cs-free LaB-driven ion source and 20 units of 324 MHz klystrons. As of June 2008, the operation times are about 3,000 and 6,000 hours for the ion source and the RF source, respectively. The operating experience of the linac is described.

Pulse-by-pulse switching of beam loading compensation in J-PARC linac LLRF

Kobayashi, Tetsuya; Anami, Shozo*; Michizono, Shinichiro*; Fang, Z.*; Suzuki, Hiroyuki; Yamaguchi, Seiya*; Chishiro, Etsuji

Proceedings of 5th Annual Meeting of Particle Accelerator Society of Japan and 33rd Linear Accelerator Meeting in Japan (CD-ROM), p.488 - 490, 2008/00

For the J-PARC linac low level RF system, in order to compensate beam-loading change by pulses in the operation of 25-Hz repetition, a function that switches the feed-forward control parameters in every pulse were installed into the digital accelerating-field control system. The linac provides a 50-mA peak current proton beam to a 3-GeV rapid-cycling synchrotron (RCS). Then the RCS distributes the 3-GeV beam into a following 50-GeV synchrotron (main ring, MR) and the Materials and Life Science Facility (MLF), which is one of the experimental facilities in the J-PARC. The 500-us long macro pulses from the ion source of the linac should be chopped into medium pulses for injection into the RCS. The duty (width or repetition) of the medium pulse depends on which facility the RCS provides the beam to the MR or MLF. Therefore the beam loading compensation needs to be corrected for the change of the medium pulse duty in the 25-Hz operation.