Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Suzuki, Sadaaki; Seki, Masami; Shinozaki, Shinichi; Sato, Fumiaki; Hiranai, Shinichi; Ishii, Kazuhiro*; Hasegawa, Koichi; Moriyama, Shinichi
JAEA-Technology 2007-055, 27 Pages, 2007/09
JAEA-Technology-2007-055.pdf:4.18MB
In the experiments featuring lower hybrid range of frequency (LHRF) system in JT-60U, carbon grills were attached to the plasma-facing part of the antenna in order to avoid the damage by the excessive heat load from the plasma. However some electric discharge traces were found there in the observation after the experiments. To avoid such discharges, improvements of the arc detector and the protection interlock by visible picture detection were tackled. In the arc detector, the amplification circuit was improved in order to obtain shorter response time and higher resolution of optical detection. Moreover, in visible picture detection, a new function of RF-on/off control utilizing PC image processing was added to distinguish the light of the arc from one of the plasma. This report summarizes improvement of the protection interlock device in a LHRF heating system.
Yokokura, Kenji; Moriyama, Shinichi; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Ishii, Kazuhiro*; Sato, Fumiaki
JAEA-Technology 2007-045, 22 Pages, 2007/07
JAEA-Technology-2007-045.pdf:6.1MB
A power measuring device using a dielectric disk for a high power millimeter waves is investigated. In the device, a high power wave is transmitted in a waveguide and then heats a dielectric installed in the waveguide. The transmitted power is estimated from the temperature rise of the dielectric disk. It is a new type of power measurement device, which is not sensitive to higher modes or change of their polarization in time. It also can measure the wide power range of kW to MW levels flexibly by choosing dielectric material proper to the power level as a detector. In the report, materials that have small dielectric loss for millimeter wave are chosen, and their properties of temperature rise and millimeter wave power capacity are estimated. On the basis of these results, design of the power measurement device and fabrication of its prototype are described for practical use in the electron cyclotron heating systems for the JT-60U and JT-60SA.
Ishii, Kazuhiro; Seki, Masami; Shinozaki, Shinichi; Hasegawa, Koichi; Hiranai, Shinichi; Suzuki, Sadaaki; Sato, Fumiaki; Moriyama, Shinichi; Yokokura, Kenji
JAEA-Technology 2007-036, 30 Pages, 2007/07
JAEA-Technology-2007-036.pdf:17.06MB
The lower hybrid (LH) antenna in JT-60U has interaction with plasmas because it should be close to them in order to inject effectively radio frequency (RF) power into them. As a result, it has been a serious problem that the antenna mouth made of stainless steels was damaged due to excessive heat loads of plasmas and RF breakdowns. To solve the problem, a heat-resistant LH antenna was developed tipping carbon grills with fairly high heat resistance on the antenna mouth, and therefore reduction in damages on the mouth was expected. Power injection into plasmas was firstly performed with the heat-resistant antenna. RF conditioning was done carefully in the initial phase because RF breakdown due to outgassing from the grills might be occurred. After sufficient degassing was done through RF conditioning, RF power of about 1.6 MW 
10 sec injection was successfully injected to plasmas. Moreover it was demonstrated that it had comparably high plasma current drive capability (about 1.6 10
A/W/m
), required as a current drive LH antenna.
Namekawa, Takashi; Kawaguchi, Koichi; Koike, Kazuhiro; Haraguchi, Shingo; Ishii, Satoru
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
New concepts of future fabrication system for low decontaminated transuranium (TRU) fuel was designed. It is essential to establish a remote fabrication system in the hot cell, because materials with high levels of radiation and high generation of heat are handled in the system. The configuration of the present systems including aspects related to economy was clarified through the conceptual design study. Technical feasibility of each concepts is follwiong. For oxide fuels, the simplified pelletizing method has a high technical feasibility for the process, and its expected practical use is possible at early stage, because this method is based on wealth results of a conventional method. The sphere-pack method has the advantage of lesser dispersion of the fine powder due to the use of solution and granule in the process. However this system will shoulder additional cost for the liquid waste treatment process due to need dispose of a large bulk of process liquid waste. The vipack method has the possibility of economical improvement if simplification of the process can be achieved. However this system has some problems for quality assurance etc. For the casting method of metal fuel, high economical efficiency is generally expected of small-scale facilities, although verification of fabrication of the TRU alloy slug is required. For nitride fuel, technology developments for N-15 enrichment and recycling, and nitride conversion process etc. In particular, for coated particle fuel fabrication, crucial technology developments are required on coating and assembly process.
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.
Ishii, Kazuhiro*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Igarashi, Koichi*; Takahashi, Masami*
JAERI-Tech 2003-079, 22 Pages, 2003/10
JAERI-Tech-2003-079.pdf:3.01MB
In JT-60U, the study of current drive by radio-frequency (RF) waves in lower hybrid range of frequency (LHRF) has been done as one of research and development works aiming at steady state operation of tokamaks. The main subject of hardware and technology development in this study is to develop a high power LHRF antenna, the main component of the system. The LHRF antenna is set closely to plasma to efficiently inject RF power into it. The LHRF antenna normally receives heat loads from the plasma, and it is required to inject high RF power. Then, it has become a problem that the antenna mouth was melted by excessive heat loads from plasma or it was melted and deformed by RF discharges. As a counter measurement against this, the LHRF antenna has been conditioned to improve its stand-off voltage capability. Furthermore, by monitoring the temperature of the LHRF antenna, adjusting its position, developing a injection method of power modulation even for current drive, and setting an arc sensor which picks up the RF discharge, the damage of the antenna mouth has been suppressed.
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
Igarashi, Koichi*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Ishii, Kazuhiro*; Takahashi, Masami*
JAERI-Tech 2003-030, 40 Pages, 2003/03
JAERI-Tech-2003-030.pdf:5.83MB
The JT-60U electron cyclotron heating (ECH) system can heat plasmas locally and drive a plasma current with four 1 MW-5 sec gyrotrons. The super conducting magnets (SCM) are required for oscillation of the gyrotron at a working frequency of 110 GHz. The SCM provides a high magnetic field of 4.5T at the cavity inside the gyrotron. This SCM system is characterized by (1) operation without liquid Helium owing to a 4 K-refrigerator applied to the magnetic coils, (2) easy maintenance. Operational experiences about the SCM system through a long term experiment for a high power gyrotron are very valuable. According to those operational experiences, it is clarified the 4 K-refrigerator should be renewed in oder to keep low temperature of the SCM. It is also found that 200 hours or less are required for the super conducting condition (
5K) after long stopping time of the refrigerator up to 150 hours. This is useful information for making a plan about ECH experiments.
Terakado, Masayuki; Shimono, Mitsugu; Igarashi, Koichi*; Takahashi, Masami*; Ishii, Kazuhiro*; Seki, Masami
Heisei-14-Nendo Tokyo Daigaku Sogo Gijutsu Kenkyukai Gijutsu Hokokushu, 3 Pages, 2003/03
no abstracts in English
Shimono, Mitsugu; Seki, Masami; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Kajiwara, Ken; Anno, Katsuto
NIFS-MEMO-36, p.382 - 385, 2002/06
no abstracts in English
Hiranai, Shinichi; Yokokura, Kenji; Moriyama, Shinichi; *; *; Fujii, Tsuneyuki
JAERI-Tech 98-006, 27 Pages, 1998/03
no abstracts in English
Koike, Kazuhiro; Ohshima, Hiroyuki; Ishii, Satoru; Namekawa, Takashi; Tsuji, Nobumasa*; Hashimoto, Akihiko*
no journal, ,
no abstracts in English
Moriyama, Shinichi; Yokokura, Kenji; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Ishii, Kazuhiro; Sato, Fumiaki; Tani, Takashi; Igarashi, Koichi; Shimono, Mitsugu; et al.
no journal, ,
no abstracts in English
Seki, Masami; Sawahata, Masayuki; Shinozaki, Shinichi; Hiranai, Shinichi; Suzuki, Sadaaki; Hasegawa, Koichi; Shimono, Mitsugu; Yokokura, Kenji; Ishii, Kazuhiro; Sato, Fumiaki; et al.
no journal, ,
no abstracts in English
Suzuki, Sadaaki; Hasegawa, Koichi; Shinozaki, Shinichi; Sato, Fumiaki; Hiranai, Shinichi; Ishii, Kazuhiro; Seki, Masami; Moriyama, Shinichi; Yokokura, Kenji
no journal, ,
no abstracts in English
Moriyama, Shinichi; Fujii, Tsuneyuki; Seki, Masami; Sawahata, Masayuki; Suzuki, Sadaaki; Shinozaki, Shinichi; Terakado, Masayuki; Hiranai, Shinichi; Hasegawa, Koichi; Shimono, Mitsugu; et al.
no journal, ,
no abstracts in English
Hiranai, Shinichi; Yokokura, Kenji; Suzuki, Sadaaki; Terakado, Masayuki; Ishii, Kazuhiro; Sato, Fumiaki; Hasegawa, Koichi; Moriyama, Shinichi
no journal, ,
no abstracts in English
Kofu, Maiko; Yamamuro, Osamu*; Watanuki, Ryuta*; Sakakibara, Toshiro*; Kawamura, Seiko; Murai, Naoki; Nakajima, Kenji; Matsuura, Masato*; Ueki, Takeshi*; Akutsu, Kazuhiro*; et al.
no journal, ,
no abstracts in English