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Journal Articles

High density plasma calculation of J-PARC RF negative ion source

Shibata, Takanori*; Asano, Hiroyuki; Ikegami, Kiyoshi*; Naito, Fujio*; Nammo, Kesao*; Oguri, Hidetomo; Okoshi, Kiyonori; Shinto, Katsuhiro; Takagi, Akira*; Ueno, Akira

AIP Conference Proceedings 1869, p.030017_1 - 030017_11, 2017/08

 Times Cited Count:4 Percentile:5.35

From September 2014, operation of Cs-seeded, multi-cusp, Radio Frequency (RF), hydrogen negative ion source (J-PARC source) has been started. The operation for 1,000 hours of J-PARC source has been achieved with H$$^{-}$$ beam current 45 mA and duty factor of 1.25 % (0.5 msec and 25 Hz). In the present study, mechanisms of hydrogen plasma ramp-up and H$$^{-}$$ production/transport processes in the steady state (which lasts for few 100 us) are investigated by numerical modeling for RF plasma. In the simulation, charged particle (e, H$$^{+}$$, H$$_2^{+}$$, and Cs$$^{+}$$) transport, time variations of inductive and capacitive electromagnetic field, collision processes between charged and neutral (H, H$$_{2}$$) particles are solved simultaneously. The model is applied to KEK parallel computation System-A with 32 nodes and 256 GB memory in order to solve high density RF plasma up to around 10$$^{18}$$ m$$^{-3}$$ with adequate statisticity. In the presentation, time variations of plasma density distributions and average energy are shown with electromagnetic field variations.

Journal Articles

Progress in long-pulse production of powerful negative ion beams for JT-60SA and ITER

Kojima, Atsushi; Umeda, Naotaka; Hanada, Masaya; Yoshida, Masafumi; Kashiwagi, Mieko; Tobari, Hiroyuki; Watanabe, Kazuhiro; Akino, Noboru; Komata, Masao; Mogaki, Kazuhiko; et al.

Nuclear Fusion, 55(6), p.063006_1 - 063006_9, 2015/06

 Times Cited Count:28 Percentile:8.37(Physics, Fluids & Plasmas)

Significant progresses in the extension of pulse durations of powerful negative ion beams have been made to realize the neutral beam injectors for JT-60SA and ITER. In order to overcome common issues of the long pulse production/acceleration of negative ion beams in JT-60SA and ITER, the new technologies have been developed in the JT-60SA ion source and the MeV accelerator in Japan Atomic Energy Agency. As for the long pulse production of high-current negative ions for JT-60SA ion source, the pulse durations have been successfully increased from 30 s at 13 A on JT-60U to 100 s at 15 A by modifying the JT-60SA ion source, which satisfies the required pulse duration of 100 s and 70% of the rated beam current for JT-60SA. This progress was based on the R&D efforts for the temperature control of the plasma grid and uniform negative ion productions with the modified tent-shaped filter field configuration. Moreover, the each parameter of the required beam energy, current and pulse has been achieved individually by these R&D efforts. The developed techniques are useful to design the ITER ion source because the sustainment of the cesium coverage in large extraction area is one of the common issues between JT-60SA and ITER. As for the long pulse acceleration of high power density beams in the MeV accelerator for ITER, the pulse duration of MeV-class negative ion beams has been extended by more than 2 orders of magnitude by modifying the extraction grid with a high cooling capability and a high-transmission of negative ions. A long pulse acceleration of 60 s has been achieved at 70 MW/m$$^{2}$$ (683 keV, 100 A/m$$^{2}$$) which has reached to the power density of JT-60SA level of 65 MW/m$$^{2}$$.

Journal Articles

Long-pulse production of high current negative ion beam by using actively temperature controlled plasma grid for JT-60SA negative ion source

Kojima, Atsushi; Hanada, Masaya; Yoshida, Masafumi; Umeda, Naotaka; Hiratsuka, Junichi; Kashiwagi, Mieko; Tobari, Hiroyuki; Watanabe, Kazuhiro; Grisham, L. R.*; NB Heating Technology Group

AIP Conference Proceedings 1655, p.060002_1 - 060002_10, 2015/04

 Times Cited Count:6 Percentile:7.12

In this paper, the recent activities on the new test stand are reported toward demonstration of the long pulse production for 22A, 100s negative ion beams. As for the temperature control of the plasma grid, a prototype of the grid with cooling/heating by circulating a high-temperature fluorinated fluid has been improved to cover the full extraction area by using 5 segments of the PG. These grids were found to have a capability to control the temperature with a time constant of 10s as well as the prototype grid. As a result, 15A negative ion beams for 100s have been achieved.

Journal Articles

Beam deflection by plasma grid filter current in the negative-ion source for JT-60U neutral beam injection system

Umeda, Naotaka; Ikeda, Yoshitaka; Hanada, Masaya; Inoue, Takashi; Kawai, Mikito; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Oga, Tokumichi

Review of Scientific Instruments, 77(3), p.03A529_1 - 03A529_3, 2006/03

 Times Cited Count:5 Percentile:67.96(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Development of an H$$^{-}$$-ion source for the High-Intensity Proton Accelerator (J-PARC)

Oguri, Hidetomo; Ueno, Akira; Namekawa, Yuya*; Ikegami, Kiyoshi*

Review of Scientific Instruments, 77(3, Part2), p.03A517_1 - 03A517_3, 2006/03

 Times Cited Count:5 Percentile:67.96(Instruments & Instrumentation)

The J-PARC Project was started in 2001 as a joint project carried out by JAERI and KEK. At the first stage of the J-PARC, the linac will accelerate the H- ion beam current of 30 mA with a duty factor of 1.25 %. The J-PARC H- ion source driven with a LaB6 filament has regularly delivered more than 35 mA beam with a duty factor of 0.9 % without resorting to cesium. Although the operated duty factor is about 1/3 of the requirement, the filament is not replaced for a half year. At the J-PARC, the lifetime of the tungsten (W) filament was measured by using another H- ion source, which can produce a 72 mA with cesium seeded. The experimental results showed that there is a possibility of the W filament satisfying the lifetime of more than 500 hours, which is J-PARC requirement. We consider the W driven plasma ion source is one of the candidates for the J-PARC source. At present, we are performing the beam test of the cesium free ion source driven with W. We will present the experimental data of the beam test in this conference.

Journal Articles

Recent progress of negative ion based neutral beam injector for JT-60U

Umeda, Naotaka; Yamamoto, Takumi; Hanada, Masaya; Grisham, L. R.*; Kawai, Mikito; Oga, Tokumichi; Akino, Noboru; Inoue, Takashi; Kazawa, Minoru; Kikuchi, Katsumi*; et al.

Fusion Engineering and Design, 74(1-4), p.385 - 390, 2005/11

 Times Cited Count:9 Percentile:43.23(Nuclear Science & Technology)

In negative ion based neutral beam injector (N-NBI) for JT-60U, some modifications for extent pulse duration from 10 second, which is design value, to 30 second was conducted. Main limit to prevent pulse extension was heat loads onto grounded grid in an ion source and onto beam limiter placed at 22 m from the ion source. To reduce these heat loads, beam extraction area was optimized and the limiter was changed to one which had about twice thermal capacity. As a result of these modifications, the temperature rise of the water which was cooling grounded grid could be suppressed under 40 degree, which can operate in steady state condition. The temperature rise of the limiter could be restricted to 60%. Untill now the beam pulse extended to 17 second of 1.6MW power at 366keV energy, and injection of 30 seconds will be achieved in next experiment.

Journal Articles

Experimental validation of beam particle self interaction in JT-60U by use of N-NB

Okano, Kunihiko*; Suzuki, Takahiro; Umeda, Naotaka; Hiwatari, Ryoji*; Masaki, Kei; Tobita, Kenji; Fujita, Takaaki

Purazuma, Kaku Yugo Gakkai-Shi, 81(8), p.579 - 580, 2005/08

In a toroidal system, circulating fast ions generated by neutral beam injection affect the beam stopping cross-section of the neutral beam itself. This effect is called "beam particle self-interaction (BPSI)". In a recent experiment in JT-60U with 350 keV H$$^{0}$$ beam, an indication of this BPSI effect has been found for the first time. In a low density discharge at about 1$$times$$10$$^{19}$$m$$^{-3}$$, the beam shine-through decreased by about 35% within several hundred msec after beam injection. This result is consistent with a prediction by the BPSI theory.

Journal Articles

Instability in the frequency range of Alfv$'e$n eigenmodes driven by negative-ion-based neutral beams in JT-60U

Shinohara, Koji; Ishikawa, Masao; Takechi, Manabu; Kusama, Yoshinori; Todo, Yasushi*; Gorelenkov, N. N.*; Cheng, C. Z.*; Fukuyama, Atsushi*; Kramer, G.*; Nazikian, R. M.*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 81(7), p.547 - 552, 2005/07

In the bursting instabilities in the frequency range of Alfven Eigenmode, we observed two types of modes phenomenologically. In one type, the time scale of the mode was $$<$$1ms and the mode amplitude was so large that we were able to detect apparent enhanced transport of the energetic ions. The enhanced transport showed the clear energy dependence by using new diagnostics, natural diamond detector. In another type, the mode amplitude is not so large, compared with the first type. The frequency up-down chirping is clearly observed with the time-scale of a few ms. This frequency chirping was reproduced by the newly developed simulation code, MEGA To demonstrate this model of Reversed-Shear-induced Alfven Eigenmode, RSAE, we have performed experiments in the condition where we can have q profile with a good signal-to-noise ratio. We observed the slow up-frequency sweeping of RSAE due to the down evolution of qmin, We have analyzed this experiment by using NOVA-K code. We observed that the most unstable mode localized around qmin.

Journal Articles

Energetic neutral particle measurement with natural diamond detector in JT-60U

Kusama, Yoshinori; Ishikawa, Masao; Takechi, Manabu; Nishitani, Takeo; Morioka, Atsuhiko; Sasao, Mamiko*; Isobe, Mitsutaka*; Krasilnikov, A.*; Kaschuck, Y.*

Proceedings of Plasma Science Symposium 2005/22nd Symposium on Plasma Processing (PSS-2005/SPP-22), p.395 - 396, 2005/00

The energetic neutral particles have been successfully measured with a natural diamond detector in the neutron and $$gamma$$ ray radiation circumstance of the JT-60U deuterium discharges. The diamond detector was covered with polyethylene and lead in order to reduce the neutron and $$gamma$$ ray background. The shield has shown expected shielding capability. A rapid increase in neutral particles has been observed at the onset of the Toroidal Alfven Eigenmode (TAE) excited by the negative-ion-based neutral beam injection. The energy range of increased neutral particles has agreed well with that predicted from the resonant interaction between the energetic ions and the TAE.

Journal Articles

Present status of development on 500keV negative ion source

Yamamoto, Takumi; Oga, Tokumichi; Kawai, Mikito; Akino, Noboru; Kazawa, Minoru; Umeda, Naotaka

Heisei-16-Nen Denki Gakkai Zenkoku Taikai Koen Rombunshu, 219 Pages, 2004/00

In JAERI, 10 MW and 500 keV negative-ion based neutral beam injection (N-NBI) system for JT-60U was constructed in 1996, in order to study a plasma heating and current drive in high-density plasma by high-energy beam injection. Thereafter, improvement of beam performance has been carried out while N-NBI system was available for experiments on JT-60U. The maximum beam energy of 418 keV and the maximum injection power of 6.2 MW have been achieved with a hydrogen beam, so far. In addition, 10 seconds of injection pulse duration, which is the designed value, was attained at the injection power of 2.6MW. Further improvement is required for the performance to reach to the final targets. It was made it clear that the performance was limited by the withstanding voltage of acceleration and heat load on acceleration grids in the ion source.

Journal Articles

Improvement of beam performance in the negative-ion based NBI system for JT-60U

Umeda, Naotaka; Grisham, L. R.*; Yamamoto, Takumi; Kuriyama, Masaaki; Kawai, Mikito; Oga, Tokumichi; Mogaki, Kazuhiko; Akino, Noboru; Yamazaki, Haruyuki*; Usui, Katsutomi; et al.

Nuclear Fusion, 43(7), p.522 - 526, 2003/07

 Times Cited Count:37 Percentile:24.34(Physics, Fluids & Plasmas)

The Negative-ion based Neutral Beam Injection System (N-NBI) for JT-60U has been operating for plasma heating and non-inductive current drive since 1996. The target is inject of neutral beam into plasma with beam energy 500 keV, injection power 10 MW, for 10 seconds. Until now pulse duration time was restricted up to 5.3 seconds because of larger heat load of port limiter. Recently from the measurement of beam profile at 3.5m downstream from the ion source, it was found that the outermost beamlets in each segment were deflected outward. It was caused by non-uniform electric field by grooves. By improving this, outermost beamlet deflection angle was decreased from 14 mrad to 4 mrad. In this result, 10 seconds injection, which is target parameter, has achieved at 355 keV, 2.6MW, while pulse length was restricted up to 5.3 seconds by larger heat load of port limiter.

Journal Articles

Development of high-performance discharges with transport barriers in JT-60U

Fukuda, Takeshi; JT-60 Team

Plasma Physics and Controlled Fusion, 44(12B), p.B39 - B52, 2002/12

 Times Cited Count:7 Percentile:73.78(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Recent progress of Alfv$'e$n eigenmode experiments using N-NB in JT-60U tokamak

Shinohara, Koji; Takechi, Manabu; Ishikawa, Masao*; Kusama, Yoshinori; Morioka, Atsuhiko; Oyama, Naoyuki; Tobita, Kenji; Ozeki, Takahisa; JT-60 Team; Gorelenkov, N. N.*; et al.

Nuclear Fusion, 42(8), p.942 - 948, 2002/08

 Times Cited Count:37 Percentile:23.68(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Beam test of the negative ion source for the high intensity proton accelerator

Shimooka, Takashi; Oguri, Hidetomo; Namekawa, Yuya*; Tomisawa, Tetsuo; Okumura, Yoshikazu; Hasegawa, Kazuo

JAERI-Tech 2002-038, 30 Pages, 2002/03

JAERI-Tech-2002-038.pdf:1.74MB

The high intensity proton accelerator facility project which is conducted jointly by JAERI and KEK is to use the secondary particles produced by nuclear spallation for various science studies. A negative hydrogen ion beam source for the accelerator is required to extract a peak beam current of more than 60 mA with a duty factor of 2.5 %. In addition, the ions should be negatively charged in order to improve the capture efficiency of the beam injected into a synchrotron. At JAERI, a negative ion source for the project has been developed with various technologies based on the large negative ion source for the nuclear fusion application. The negative ion beam current and the rms normalized emittance of 72 mA and 0.15 $$pi$$mm.mrad were achieved in the cesium seeded operation, respectively. A waveform of the pulsed beam current was sensitive to the operation gas flow rate, and became to have a good flatness at about 16 SCCM. These results show that the basic performance of the ion source satisfies the requirement of the ion source for the project.

Journal Articles

Development of an H$$^{-}$$ ion source for the high intensity proton Linac

Oguri, Hidetomo; Okumura, Yoshikazu; Hasegawa, Kazuo; Namekawa, Yuya*; Shimooka, Takashi*

Review of Scientific Instruments, 73(2), p.1021 - 1023, 2002/02

 Times Cited Count:17 Percentile:33.8(Instruments & Instrumentation)

At JAERI, a high intensity proton accelerator with a beam power of 1 MW has been proposed to pursue the nuclear-particle physics, materials and life sciences and R&D for nuclear transformation. A negative hydrogen ion source for the accelerator is required to extract a peak beam current of more than 60 mA with a normalized emittance of 0.15 pimm.mrad (rms). We have designed and tested a volume production type negative ion source to accumulate experimental data to fulfill the requirement for the accelerator. The source plasma is produced by an arc discharge using tungsten filaments. The cesium vapor is introduced into the arc chamber to enhance the beam current. The beam extractor consists of three electrodes with a single aperture of 8 mm in diameter. The negative ion beam current of 40 mA was achieved with a duty factor of 5 % at the beam energy and arc discharge power of 70 keV and 30 kW, respectively. The beam current increased linearly with the arc power in the cesium operation. The beam test by using a more powerful arc power supply is in progress.

Journal Articles

Spatial uniformity of negative ion production in volume negative ion source

Morishita, Takatoshi; Miyamoto, Kenji*; Fujiwara, Yukio*; Hanada, Masaya; Kitagawa, Tadashi*; Kashiwagi, Mieko; Okumura, Yoshikazu; Watanabe, Kazuhiro

Review of Scientific Instruments, 73(2), p.1064 - 1066, 2002/02

 Times Cited Count:2 Percentile:79.89(Instruments & Instrumentation)

no abstracts in English

Journal Articles

High current negative ion production in a low-pressure discharge

Morishita, Takatoshi; Kashiwagi, Mieko; Okumura, Yoshikazu; Watanabe, Kazuhiro; Hanada, Masaya; Inoue, Takashi; Imai, Tsuyoshi

Dai-12-Kai Ryushisen No Sentanteki Oyo Gijutsu Ni Kansuru Shimpojiumu (BEAMS 2001) Hobunshu, p.33 - 36, 2001/11

no abstracts in English

Journal Articles

Long pulse production of high density negative(H$$^{-}$$/D$$^{-}$$) ion beams in negative ion source development for NBI

Kashiwagi, Mieko; Amemiya, Toru*; Iga, Takashi*; Inoue, Takashi; Imai, Tsuyoshi; Okumura, Yoshikazu; Takayanagi, Tomohiro; Hanada, Masaya; Fujiwara, Yukio; Morishita, Takatoshi; et al.

Dai-12-Kai Ryushisen No Sentanteki Oyo Gijutsu Ni Kansuru Shimpojiumu (BEAMS 2001) Hobunshu, p.37 - 40, 2001/11

no abstracts in English

Journal Articles

Exploration of fusion energy; JT-60 develops the ITER steady-state operation

Kawano, Yasunori; Kusama, Yoshinori

Genshiryoku eye, 47(11), p.29 - 33, 2001/11

no abstracts in English

Journal Articles

Development of fusion energy with vaccuum technology

Watanabe, Kazuhiro

Denki Gakkai-Shi, 121(6), p.384 - 386, 2001/06

no abstracts in English

55 (Records 1-20 displayed on this page)