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Journal Articles

Improvement in quantitative performance of underwater laser-induced breakdown spectroscopy based on the understanding of laser ablation phenomena

Matsumoto, Ayumu

Reza Kako Gakkai-Shi, 23(3), p.222 - 231, 2016/10

no abstracts in English

Journal Articles

Impact of wall saturation on particle control in long and high-power-heated discharges in JT-60U

Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Kubo, Hirotaka; Miura, Yukitoshi; Shimizu, Katsuhiro; Konoshima, Shigeru; Masaki, Kei; Higashijima, Satoru; JT-60 Team

Nuclear Fusion, 46(5), p.626 - 634, 2006/05

 Times Cited Count:19 Percentile:56.94(Physics, Fluids & Plasmas)

In order to understand plasma-wall interactions in a long time scale, the discharge pulse length has been extended from 15 s to 65 s, with the NB-heating duration extended to 30 s. Nearly-saturation of the divertor plates was observed in the latter half of long pulse ELMy H-mode discharges. Particle sink into the divertor plates gradually decreased, and subsequently, wall-pumping efficiency became zero. This wall saturation resulted in a rise of the main plasma density without any auxiliary particle supply besides NB with divertor-pumping. Even when the total injected energy reached up to $$sim$$ 350 MJ in a discharge, neither sudden increase of carbon generation such as carbon bloom nor increase of the dilution of the main plasma was observed.

Journal Articles

Development and contribution of RF heating and current drive systems to long pulse, high performance experiments in JT-60U

Moriyama, Shinichi; Seki, Masami; Terakado, Masayuki; Shimono, Mitsugu; Ide, Shunsuke; Isayama, Akihiko; Suzuki, Takahiro; Fujii, Tsuneyuki; JT-60 Team

Fusion Engineering and Design, 74(1-4), p.343 - 349, 2005/11

 Times Cited Count:7 Percentile:47.08(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Overview of JT-60U progress towards steady-state advanced tokamak

Ide, Shunsuke; JT-60 Team

Nuclear Fusion, 45(10), p.S48 - S62, 2005/10

 Times Cited Count:51 Percentile:84.74(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Actively-cooled plasma electrode for long pulse operations in a cesium-seeded negative ion source

Fujiwara, Yukio; Watanabe, Kazuhiro; Okumura, Yoshikazu; Trainham, R.*; Jacquot, C.*

Review of Scientific Instruments, 76(1), p.013501_1 - 013501_5, 2005/01

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

A new actively-cooled plasma electrode has been developed for long pulse operation in a cesium-seeded negative ion source. To keep the electrode temperature at about 300 $$^{circ}$$C, which is optimum range of temperature to enhance cesium effects, the electrode cooling structure has been designed using three-dimensional numerical simulation assuming that the heat flux from the source plasma was 15 W/cm$$^{2}$$. Water cooling tubes were brazed to the plasma electrode substrate with spacers made of stainless steel which acts as a thermal resistance. The fabricated plasma electrode has been tested in a cesium-seeded volume negative ion source called Kamaboko source. The temperature of the electrode reached 280 $$^{circ}$$C for the arc power of 41 kW, which is operating condition required for producing D- beams with current densities exceeding 20 mA/cm$$^{2}$$. It was demonstrated that the actively-cooled plasma electrode is applicable to long pulse operations, meeting the temperature requirement for optimizing the surface-production process of negative ions in the cesium seeded ion source.

Journal Articles

Study of millimeter wave high-power gyrotron for long pulse operation

Kasugai, Atsushi; Sakamoto, Keishi; Minami, Ryutaro; Takahashi, Koji; Imai, Tsuyoshi

Nuclear Instruments and Methods in Physics Research A, 528(1-2), p.110 - 114, 2004/08

 Times Cited Count:23 Percentile:82.19(Instruments & Instrumentation)

The development of the millimeter wave high power gyrotron with the development of a depressed collector, an over sized cavity and a synthesized diamond output window is under going in JAERI. The performances of 170 GHz, 0.9 MW for 9.2 s and 0.5 MW for 30 s were achieved up to now. It was clarified, however, that pulse extension of the gyrotron was limited by sudden outgassing due to stray RF power deposition to the bellows behind movable mirror. For suppression of stray RF power deposition, the structure of the bellows section was improved to avoid the direct power deposition and the surface of bellows was coated by copper for reduction of RF loss and increase of thermal conductivity. As a result of the modification, temperature increase of bellows was reduced to less than 1/10 and time constant of thermal diffusion shortened to 90 s from 270 s in comparison with before the modification. This indicates that the modification is quite effective for suppression of temperature increase.

JAEA Reports

Performance and experience of a 110 GHz gyrotron operation on the JT-60U ECH system

Takahashi, Masami*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Kasugai, Atsushi

JAERI-Tech 2003-080, 27 Pages, 2003/11

JAERI-Tech-2003-080.pdf:3.11MB

The JT-60U electron cyclotron heating (ECH) system has been introduced to suppress MHD instabilities via a current profile control by local heating or current drive. The ECH system consists of four 1MW-110GHz gyrotrons, four 60m transmission lines composed of a corrugated waveguide with a diameter of 31.75mm and two steerable type mirror antennas. Recently, a gyrotron developed for ITER has realized high power in an extremely high frequency range of millimeter waves although there was no high power source around 110GHz ten years ago. Therefore, it requires many techniques to operate the gyrotoron. The oscillation conditions had to be found at output power 1MW by adjusting the magnetic field parameters and anode voltage after heater aging. Then conditioning of the gyrotoron was done, where the pulse length is gradually extended in order to operate for 1sec level of pulse length. Consequently, 1MW-5sec of the designed value was achieved and the ECH system with four gyrotrons successfully injected the millimeter wave energy of 10MJ into plasmas, which is the world record.

JAEA Reports

Low-power and long-pulse test of a klystron of the JT-60U LHRF heating system

Shimono, Mitsugu; Seki, Masami; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Takahashi, Masami*; Shinozaki, Shinichi; Hiranai, Shinichi; Sato, Fumiaki*; Anno, Katsuto

JAERI-Tech 2003-075, 29 Pages, 2003/09

JAERI-Tech-2003-075.pdf:4.62MB

no abstracts in English

Journal Articles

A Frame-cooled plasma grid for long pulse operations in a cesium-seeded volume negative ion source

Fujiwara, Yukio; Okumura, Yoshikazu; Watanabe, Kazuhiro; Trainham, R.*; Jacquot, C.*

Review of Scientific Instruments, 73(2), p.298 - 304, 2002/02

 Times Cited Count:4 Percentile:30.26(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Long pulse operation of the JAERI superconducting RF linac for FEL

Minehara, Eisuke; Sugimoto, Masayoshi; Sawamura, Masaru; Nagai, Ryoji; Kikuzawa, Nobuhiro; Nishimori, Nobuyuki; *

Proc. of 11th Symp. on Accelerator Sci. and Technol., P. 120, 1997/00

no abstracts in English

Journal Articles

High power negative ion beam development for heating and current drive in fusion plasmas

Watanabe, Kazuhiro; Hanada, Masaya; Inoue, Takashi; *; Mizuno, Makoto; Ohara, Yoshihiro; Okumura, Yoshikazu; Suzuki, Yasuo*; Tanaka, Hideki*; Tanaka, Masanobu*

Proc. of 14th Int. Conf. on Plasma Physics and Controlled Nuclear Fusion Research, p.371 - 378, 1993/00

no abstracts in English

Journal Articles

Long pulse operation of a cesium‐seeded multicusp H$$^{-}$$ ion source

Okumura, Yoshikazu; Hanada, Masaya; Inoue, Takashi; Mizuno, Makoto; Ohara, Yoshihiro; Suzuki, Yasuo*; Tanaka, Hideki*; Tanaka, M.*; Watanabe, Kazuhiro

Review of Scientific Instruments, 63(4), p.2708 - 2710, 1992/04

 Times Cited Count:23 Percentile:86.52(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

Extraction of 10sec/75keV/70A Ion Beams at Prototype Neutral Beam Injector Unit for JT-60

; Araki, Masanori; ; ; ; ; ; Matsuda, Shinzaburo; ; *; et al.

JAERI-M 82-045, 13 Pages, 1982/05

JAERI-M-82-045.pdf:0.66MB

no abstracts in English

Journal Articles

Production of 75keV,70A,10sec ion beams

; Araki, Masanori; ; ; ; ; ; Matsuda, Shinzaburo; ; *; et al.

Review of Scientific Instruments, 53(12), p.1864 - 1869, 1982/00

 Times Cited Count:20 Percentile:88.27(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Measurement of impurities in a long-pulse,multiampere hydrogen beam

; Mizutani, Yasuhiko*; Ohara, Yoshihiro;

Review of Scientific Instruments, 52(1), p.1 - 7, 1981/00

 Times Cited Count:17 Percentile:86.97(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

Preliminary Experiments of Cooled Extraction of Ion Sources for Neutral Beam Injectors

*; ; *; *;

JAERI-M 7612, 11 Pages, 1978/03

JAERI-M-7612.pdf:0.65MB

no abstracts in English

Oral presentation

Fiber-optic laser-induced breakdown spectroscopy of solid samples in air with long nanosecond pulse

Matsumoto, Ayumu; Oba, Hironori; Toshimitsu, Masaaki; Akaoka, Katsuaki; Wakaida, Ikuo

no journal, , 

Oral presentation

Expansion dynamics of laser-produced plasma in long-pulse fiber-optic LIBS of metal target in air

Matsumoto, Ayumu; Oba, Hironori; Akaoka, Katsuaki; Wakaida, Ikuo

no journal, , 

Oral presentation

Basic R&D on decommissioning of Fukushima Daiichi Nuclear Power Station and application of Laser Remote Analysis for in-core and in-situ monitoring of debris

Wakaida, Ikuo; Oba, Hironori; Akaoka, Katsuaki; Oba, Masaki; Matsumoto, Ayumu; Miyabe, Masabumi; Ikeda, Yuji*; Sakka, Tetsuo*; Taira, Takunori*

no journal, , 

For the decommissioning of "Fukushima Daiichi Nuclear Power Station (F1NPS)", widely basic R&D and matting for actual application for decommissioning technology will be strongly required. CLADS/JAEA is one of the key institute for strategic promotion of Decommissioning Science on F1NPS. As for the development of rapid, easy, onsite and in-situ remote diagnostic/analysis techniques under extremely high radioactive condition, the concept of probing by light and diagnostic by light with radiation resistant optical fiber will be one of the simple, powerful and applicable choices as the innovative development based on laser induced breakdown spectroscopy (LIBS) technology. Optical fiber based LIBS is developed for in-core and in-situ elemental analysis of debris and its activity is performed under severe environmental conditions such as high radiation field of about 10kGy/h and under water. Long pulse laser, microwave assisted LIBS and microchip laser are also introduced for more high sensitivity.

Oral presentation

Advanced study on remote and in-situ elemental analysis of molten fuel debris in damaged core by innovative optical spectroscopy

Wakaida, Ikuo; Oba, Hironori*; Ikeda, Yuji*; Sakka, Tetsuo*; Taira, Takunori*

no journal, , 

Radiation resistant optical fiber based laser induced breakdown spectroscopy (Fiber LIBS) is developed for in-core and in-situ elemental analysis of debris and its activity is performed under severe environmental conditions such as high radiation field of about 10kGy/h and under water. Long pulse laser, microwave assisted LIBS for more high sensitivity and micro-chip Laser will be also introduced for In-Core use optical source.

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