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Journal Articles

22A beam production of the uniform negative ions in the JT-60 negative ion source

Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Kashiwagi, Mieko; Grisham, L. R.*; Hatayama, Akiyoshi*; Shibata, Takanori*; Yamamoto, Takashi*; Akino, Noboru; Endo, Yasuei; et al.

Fusion Engineering and Design, 96-97, p.616 - 619, 2015/10

 Times Cited Count:10 Percentile:73.32(Nuclear Science & Technology)

In JT-60 Super Advanced for the fusion experiment, 22A, 100s negative ions are designed to be extracted from the world largest ion extraction area of 450 mm $$times$$ 1100 mm. One of the key issues for producing such as high current beams is to improve non-uniform production of the negative ions. In order to improve the uniformity of the negative ions, a tent-shaped magnetic filter has newly been developed and tested for JT-60SA negative ion source. The original tent-shaped filter significantly improved the logitudunal uniformity of the extracted H$$^{-}$$ ion beams. The logitudinal uniform areas within a $$pm$$10 deviation of the beam intensity were improved from 45% to 70% of the ion extraction area. However, this improvement degrades a horizontal uniformity. For this, the uniform areas was no more than 55% of the total ion extraction area. In order to improve the horizontal uniformity, the filter strength has been reduced from 660 Gasus$$cdot$$cm to 400 Gasus$$cdot$$cm. This reduction improved the horizontal uniform area from 75% to 90% without degrading the logitudinal uniformity. This resulted in the improvement of the uniform area from 45% of the total ion extraction areas. This improvement of the uniform area leads to the production of a 22A H$$^{-}$$ ion beam from 450 mm $$times$$ 1100 mm with a small amount increase of electron current of 10%. The obtained beam current fulfills the requirement for JT-60SA.

Journal Articles

Non-destructive examination of jacket sections for ITER central solenoid conductors

Takahashi, Yoshikazu; Suwa, Tomone; Nabara, Yoshihiro; Ozeki, Hidemasa; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4200904_1 - 4200904_4, 2015/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

The Japan Atomic Energy Agency (JAEA) is responsible for procuring all amounts of Central Solenoid (CS) Conductors for ITER, including CS jacket sections. The conductor is cable-in-conduit conductor (CICC) with a central spiral. A total of 576 Nb$$_{3}$$Sn strands and 288 copper strands are cabled around the central spiral. The maximum operating current is 40 kA at magnetic field of 13 T. CS jacket section is circular in square type tube made of JK2LB, which is high manganese stainless steel with boron added. Unit length of jacket sections is 7 m and 6,300 sections will be manufactured and inspected. Outer/inner dimension and weight are 51.3/35.3 mm and around 90 kg, respectively. Eddy Current Test (ECT) and Phased Array Ultrasonic Test (PAUT) were developed for non-destructive examination. The defects on inner and outer surfaces can be detected by ECT. The defects inside jacket section can be detected by PAUT. These technology and the inspected results are reported in this paper.

JAEA Reports

Disassembly of the NBI system on JT-60U for JT-60 SA

Akino, Noboru; Endo, Yasuei; Hanada, Masaya; Kawai, Mikito*; Kazawa, Minoru; Kikuchi, Katsumi*; Kojima, Atsushi; Komata, Masao; Mogaki, Kazuhiko; Nemoto, Shuji; et al.

JAEA-Technology 2014-042, 73 Pages, 2015/02

JAEA-Technology-2014-042.pdf:15.1MB

According to the project plan of JT-60 Super Advanced that is implemented as an international project between Japan and Europe, the neutral beam (NB) injectors have been disassembled. The disassembly of the NB injectors started in November, 2009 and finished in January, 2012 without any serious problems as scheduled. This reports the disassembly activities of the NB injectors.

JAEA Reports

Development of the control system with versatile PLCs for the long-pulse negative ion source

Komata, Masao; Shimizu, Tatsuo; Ozeki, Masahiro; Kojima, Atsushi; Hanada, Masaya

JAEA-Technology 2014-041, 50 Pages, 2015/01

JAEA-Technology-2014-041.pdf:22.68MB

In JT-60 Super Advanced, the machine for nuclear fusion research with superconducting magnets for long pulse operation, the negative-ion-base neutral beam injector is required to extend the pulse duration time 10 s to 100 s. In order to realize the long-pulse N-NB injector, the control system of the power supplies for the negative ion source has been newly developed. The control system with use of the versatile devices such as PLC was designed for an ease extension of the functions. Since the control system should have the many different functions which require the wide range of the sampling time of 1 milli-second to 10, all of the functions are performed by distributing PLCs for each of the function. The developed control system has been applied in the tests of the JT-60 negative ion source, where a 100 s negative ion beam has been successfully produced. Through this test, the controllability of this system has been confirmed to be feasible for JT-60SA operation.

Journal Articles

Establishment of production process of JK2LB jacket section for ITER CS

Ozeki, Hidemasa; Hamada, Kazuya; Takahashi, Yoshikazu; Nunoya, Yoshihiko; Kawano, Katsumi; Oshikiri, Masayuki; Saito, Toru; Teshima, Osamu*; Matsunami, Masahiro*

IEEE Transactions on Applied Superconductivity, 24(3), p.4800604_1 - 4800604_4, 2014/06

 Times Cited Count:14 Percentile:64(Engineering, Electrical & Electronic)

Journal Articles

Cabling technology of Nb$$_3$$Sn conductor for ITER central solenoid

Takahashi, Yoshikazu; Nabara, Yoshihiro; Ozeki, Hidemasa; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; Uno, Yasuhiro; et al.

IEEE Transactions on Applied Superconductivity, 24(3), p.4802404_1 - 4802404_4, 2014/06

 Times Cited Count:20 Percentile:73.53(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency (JAEA) is procuring all amounts of Nb$$_3$$Sn conductors for Central Solenoid (CS) in the ITER project. Before start of mass-productions, the conductor should be tested to confirm superconducting performance in the SULTAN facility, Switzerland. The original design of cabling twist pitches is 45-85-145-250-450 mm, called normal twist pitch (NTP). The test results of the conductors with NTP was that current shearing temperature (Tcs) is decreasing due to electro-magnetic (EM) load cycles. On the other hand, the results of the conductors with short twist pitches (STP) of 25-45-80-150-450 mm show that the Tcs is stabilized during EM load cyclic tests. Because the conductors with STP have smaller void fraction, higher compaction ratio during cabling is required and possibility of damage on strands increases. The technology for the cables with STP was developed in Japanese cabling suppliers. The several key technologies will be described in this paper.

Journal Articles

Improvement of uniformity of the negative ion beams by Tent-shaped magnetic field in the JT-60 negative ion source

Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Kashiwagi, Mieko; Grisham, L. R.*; Akino, Noboru; Endo, Yasuei; Komata, Masao; Mogaki, Kazuhiko; Nemoto, Shuji; et al.

Review of Scientific Instruments, 85(2), p.02B314_1 - 02B314_4, 2014/02

 Times Cited Count:12 Percentile:55.08(Instruments & Instrumentation)

Non-uniformity of the negative ion beams in the JT-60 negative ion source was improved by modifying an external magnetic field to a tent-shaped magnetic field for reduction of the local heat loads in the source. Distributions of the source plasmas (H$$^{+}$$ ions and H$$^{0}$$ atoms) of the parents of H$$^{-}$$ ions converted on the cesium covered plasma grids were measured by Langmuir probes and emission spectroscopy. Beam intensities of the H$$^{-}$$ ions extracted from the plasma grids were measured by IR camera from the back of the beam target plate. The tent-shaped magnetic field prevented the source plasmas to be localized by B $$times$$ grad B drift of the primary electrons emitted from the filaments in the arc chamber. As a result, standard derivation of the H$$^{-}$$ ions beams was reduced from 14% (the external magnetic field) to 10% (the tent-shaped magnetic field) without reduction of an activity of the H$$^{-}$$ ion production.

Journal Articles

Origin of non-uniformity of the source plasmas in JT-60 negative ion source

Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Inoue, Takashi; Kashiwagi, Mieko; Grisham, L. R.*; Akino, Noboru; Endo, Yasuei; Komata, Masao; Mogaki, Kazuhiko; et al.

Plasma and Fusion Research (Internet), 8(Sp.1), p.2405146_1 - 2405146_4, 2013/11

Distributions of H$$^{0}$$ and H$$^{+}$$ in the source plasmas produced at the end-plugs of JT-60 negative ions source were measured by Langmuir probes and emission spectroscopy in order to experimentally investigate the cause of lower density of the negative ions extracted from end-plugs in the source. Densities of H$$^{0}$$ and H$$^{+}$$ in end-plugs of the plasma grid in the source were compared with those in the center regions. As a result, lower density of the negative ion at the edge was caused by lower beam optics due to lower and higher density of the H$$^{0}$$ and H$$^{+}$$.

Journal Articles

Progress of high-power and long-pulse ECRF system development in JT-60

Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Sato, Fumiaki; et al.

Nuclear Fusion, 51(10), p.103037_1 - 103037_10, 2011/10

 Times Cited Count:18 Percentile:63.67(Physics, Fluids & Plasmas)

A new gyrotron operation technique to increase oscillation efficiency was developed on the JT 60 ECRF system. The electron pitch factor was optimized by controlling anode voltage within 0.1 s after the start of the operation. By applying this technique, the gyrotron output power of 1.5 MW for 4 s was recorded, for the first time. The reduced collector heat load at 1.5 MW operations was reduced by 20% and it will be acceptable for longer pulse operation. A new gyrotron with an improved mode converter was developed in order to demonstrate reduction of the stray radiation which had limited the pulse length. The stray radiation was reduced to 1/3 of that of the original gyrotron. A conditioning operation of the improved gyrotron is proceeding up to 31 s at 1 MW. These progresses significantly contribute to enhancing the high power and long pulse capability of the ECRF system toward JT 60SA.

Journal Articles

Progress in JT-60 joint research

Kimura, Haruyuki; Inutake, Masaaki*; Kikuchi, Mitsuru; Ogawa, Yuichi*; Kamada, Yutaka; Ozeki, Takahisa; Naito, Osamu; Takase, Yuichi*; Ide, Shunsuke; Nagasaki, Kazunobu*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 83(1), p.81 - 93, 2007/01

no abstracts in English

Journal Articles

Development of completely Solenoidless tokamak operation in JT-60U

Ushigome, Masahiro*; Ide, Shunsuke; Ito, Satoshi*; Jotaki, Eriko*; Mitarai, Osamu*; Shiraiwa, Shunichi*; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; Fujita, Takaaki; et al.

Nuclear Fusion, 46(2), p.207 - 213, 2006/02

 Times Cited Count:11 Percentile:39.31(Physics, Fluids & Plasmas)

This papaer studies on tokamak plasma start-up completely without central solenoid (CS). On the JT-60 tokamak it is demonstrated that a completely CS-less Ip start-up to 100 kA was achieved even without any null-point by Electron cyclotron range of frequencies (ECRF) and outer PF coil current swing only. Necessary conditions (the EC power, the toroidal field etc.) were clarified. Moreover, it was succeded to maintain Ip = 260kA for 1 sec without CS by NB only. In addition Ip ramp-up by EC and NB only (without LHCD) from 215 to 310kA was achieved. In a high confinement reversed shear discharge, a result suggesting bootstrap over drive was obtained.

Journal Articles

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

no abstracts in English

Journal Articles

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Cho, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

 Times Cited Count:33 Percentile:71.47(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Reports from Meetings of ITPA (International Tokamak Physics Activity), 4

Takamura, Shuichi*; Wakatani, Masahiro*; Ninomiya, Hiromasa; Kamada, Yutaka; Yatsu, Kiyoshi*; Hatae, Takaki; Sugihara, Masayoshi; Iio, Shunji*; Ozeki, Takahisa; Kawano, Yasunori

Purazuma, Kaku Yugo Gakkai-Shi, 79(1), P. 70, 2003/01

no abstracts in English

Journal Articles

Energetic particle experiments in JT-60U and their implications for a fusion reactor

Tobita, Kenji; Kusama, Yoshinori; Shinohara, Koji; Nishitani, Takeo; Kimura, Haruyuki; Kramer, G. J.*; Nemoto, Masahiro*; Kondoh, Takashi; Oikawa, Toshihiro; Morioka, Atsuhiko; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.315 - 326, 2002/09

 Times Cited Count:8 Percentile:49.76(Nuclear Science & Technology)

Energetic particle experiments in JT-60U are summarized, mainly covering ripple loss and Alfven eigenmodes (AE modes). Significant loss was observed for 85 keV NBI ions and fusion-produced tritons increased when toroidal field ripple at the plasma surface, especially in reversed shear plasma. Measurement of hot spots on the first wall due to ripple loss confirmed agreement with code predictions, validating the modeling incorporated in an orbit-following Monte Carlo code. A variety of AE modes were destabilized in ICRF minority heating and negative-ion-based NBI (N-NBI) heating. Most of the observed modes are gap modes identified to be TAE, EAE and NAE. Interesting finding is pulsating modes accompanying frequency sweep, which were destabilized by N-NBI and sometimes induced a beam ion loss of up to 25%. Also presented are energetic particle issues in auxiliary heating with ICRF and N-NBI.

Journal Articles

Fusion plasma performance and confinement studies on JT-60 and JT-60U

Kamada, Yutaka; Fujita, Takaaki; Ishida, Shinichi; Kikuchi, Mitsuru; Ide, Shunsuke; Takizuka, Tomonori; Shirai, Hiroshi; Koide, Yoshihiko; Fukuda, Takeshi; Hosogane, Nobuyuki; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.185 - 254, 2002/09

 Times Cited Count:28 Percentile:48.48(Nuclear Science & Technology)

With the main aim of providing physics basis for ITER and the steady-state tokamak reactors, JT-60/JT-60U has been developing and optimizing the operational concepts, and extending the discharge regimes toward sustainment of high integrated performance in the reactor relevant parameter regime. In addition to achievement of the equivalent break-even condition (QDTeq up to 1.25) and a high fusion triple product = 1.5E21 m-3skeV, JT-60U has demonstrated the integrated performance of high confinement, high beta-N, full non-inductive current drive with a large fraction of bootstrap current in the reversed magnetic shear and in the high-beta-p ELMy H mode plasmas characterized by both internal and edge transport barriers. The key factors in optimizing these plasmas are profile and shape controls. As represented by discovery of various Internal Transport Barriers, JT-60/JT-60U has been emphasizing freedom and restriction of profiles in various confinement modes. JT-60U has demonstrated applicability of these high confinement modes to ITER and also clarified remaining issues.

Journal Articles

Report of ITER Physics R&D Expert Group Workshop and Physics Committee Meeting

Toi, Kazuo*; Fukuda, Takeshi; Wakatani, Masahiro*; Ogawa, Yuichi*; Takizuka, Tomonori; Miura, Yukitoshi; Ide, Shunsuke; Takase, Yuichi*; Tobita, Kenji; Fukuyama, Atsushi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 77(2), p.184 - 191, 2001/02

no abstracts in English

Journal Articles

Fast particle experiments in JT-60U

Kramer, G. J.; Iwase, Makoto; Kusama, Yoshinori; Morioka, Atsuhiko; Nemoto, Masahiro; Nishitani, Takeo; Shinohara, Koji; Takeji, Satoru; Tobita, Kenji; Ozeki, Takahisa; et al.

Nuclear Fusion, 40(7), p.1383 - 1396, 2000/07

 Times Cited Count:44 Percentile:78.44(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Characteristics of Alfv$'e$n eigenmodes, burst modes and chirping modes in the Alfv$'e$n frequency range driven by negative ion based neutral beam injection in JT-60U

Kusama, Yoshinori; Kramer, G. J.; Kimura, Haruyuki; Saigusa, Mikio*; Ozeki, Takahisa; Tobita, Kenji; Oikawa, Toshihiro; Shinohara, Koji; Kondoh, Takashi; Moriyama, Shinichi; et al.

Nuclear Fusion, 39(11Y), p.1837 - 1843, 1999/11

 Times Cited Count:63 Percentile:87.19(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Destabilization of ellipticity-induced Alfven eigenmodes during ICRF heating and stabilization by negative-ion-based neutral beam injection in JT-60U

Kusama, Yoshinori; Fu, G. Y.*; Kramer, G. J.*; Saigusa, Mikio*; Oikawa, Toshihiro; Ozeki, Takahisa; Moriyama, Shinichi; Tchernychev, F. V.*; Nemoto, Masahiro; Kondoh, Takashi; et al.

Plasma Physics and Controlled Fusion, 41(9), p.1167 - 1177, 1999/00

 Times Cited Count:5 Percentile:20.82(Physics, Fluids & Plasmas)

no abstracts in English

48 (Records 1-20 displayed on this page)