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Journal Articles

Time evolution of negative ion profile in a large cesiated negative ion source applicable to fusion reactors

Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Kashiwagi, Mieko; Umeda, Naotaka; Hiratsuka, Junichi; Ichikawa, Masahiro; Watanabe, Kazuhiro; Grisham, L. R.*; Tsumori, Katsuyoshi*; et al.

Review of Scientific Instruments, 87(2), p.02B144_1 - 02B144_4, 2016/02

 Times Cited Count:9 Percentile:43.04(Instruments & Instrumentation)

Time evolution of spatial profile of negative ion production during an initial conditioning phase has been experimentally investigated in the JT-60 negative ion source. Up to 0.4 g Cs injection, there is no enhancement of the negative ion production and no observation of the Cs emission signal in the source, suggesting the injected Cs is mainly deposited on the water-cooled wall near the nozzle. After 0.4 g Cs injection, enhancement of the negative ion production appeared only at the central segment of the PG. The calculation of the Cs neutral/ion trajectories implied that a part of Cs was ionized near the nozzle and was transported to this area. The expansion of the area of the surface production was saturated after ~2 g Cs injection corresponding to 6000 s discharge time. From the results, it is found that Cs ionization and its transport plays an important role for the negative ion production.

Journal Articles

Development of a negative hydrogen ion source for spatial beam profile measurement of a high intensity positive ion beam

Shinto, Katsuhiro; Wada, Motoi*; Nishida, Tomoaki*; Demura, Yasuhiro*; Sasaki, Daichi*; Tsumori, Katsuyoshi*; Nishiura, Masaki*; Kaneko, Osamu*; Kisaki, Masashi*; Sasao, Mamiko*

AIP Conference Proceedings 1390, p.675 - 683, 2011/09

 Times Cited Count:0 Percentile:0.19

Journal Articles

A Negative ion beam probe for diagnostics of a high intensity ion beam

Shinto, Katsuhiro; Wada, Motoi*; Kaneko, Osamu*; Tsumori, Katsuyoshi*; Nishiura, Masaki*; Sasao, Mamiko*; Kisaki, Masashi*

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.999 - 1001, 2010/05

We propose a negative ion beam probe system as a new scheme to diagnose beam profile of high power positive ion beams. Two RF linacs of IFMIF have to drive the neutron source by providing continuous-wave (CW) positive deuterium ion beams with the intensity of 125 mA each at the beam energy of 40 MeV. During the CW beam operations, the extreme intensity of the beam and the severe radiation levels make the beam diagnostics with conventional techniques in the transport lines terribly difficult. A beam of negative ions liable to lose the additional electron at the occasion of impact with a high energy particle can work as a probe to measure the positive ion beam profile. On possible configuration to achieve high intensity beam profile measurement is to inject a negative ion probe beam into the target beam perpendicularly, and measure the attenuation of the negative ion beam by beam-beam interaction at each position. We have started an experimental study for the proof-of-principle of the new beam profile monitoring system. The paper presents the status quo of this beam profile monitor system development and the prospects to apply the system to the IFMIF beam line controls.

Journal Articles

Development of negative ion based neutral beam injector toward JT-60SA

Tanaka, Yutaka; Hanada, Masaya; Kobayashi, Kaoru; Kamada, Masaki; Kisaki, Masashi

Journal of Plasma and Fusion Research SERIES, Vol.8, p.1547 - 1550, 2009/09

This paper reports recent R&D results on negative ion-based NBI system for JT-60 Super Advanced where 10 MW neutral beams is designed to be injected for 100 seconds. There are major two issues to realize such as a high-power and long-pulse injection, i.e., the improvement of voltage holding capability and the reduction of the grid power loading of the JT-60U negative ion source with three acceleration stages. As the first step for improving voltage holding capability, the breakdown location has been examined on site of JT-60U by measuring the lights emitted from spark gaps that are installed outside of the ion source in parallel with acceleration stages. To reduce the grid power to an allowable level, outward deflection of outmost beamlets, due to space charge of the inner beamlets, was suppressed by distorting the acceleration electric field at the edge of the grids. This allowed to reduce the highest grid power loading to acceptable level of 5 %.

Journal Articles

Energy spectra of bremsstrahlung X-rays emitted from an FRP insulator

Tanaka, Yutaka; Ikeda, Yoshitaka; Hanada, Masaya; Kobayashi, Kaoru; Kamada, Masaki; Kisaki, Masashi; Akino, Noboru; Yamano, Yasushi*; Kobayashi, Shinichi*; Grisham, L. R.*

IEEE Transactions on Plasma Science, 37(8), p.1495 - 1498, 2009/08

 Times Cited Count:1 Percentile:4.27(Physics, Fluids & Plasmas)

Voltage holding capability of the JT-60 negative ion source is limited by surface flashover on the FRP insulator. To improve the voltage holding capability of the ion source, the understanding of the surface flashover is required. In this study, electron energy is estimated by measuring the bremsstrahlung X-ray emitted from an FRP insulator. Energy spectra of X-ray were measured for 3 different positions and compared with those of the vacuum gap between electrodes. Near the anode, X-ray spectrum was dominated by the monoenergetic electron. Near the cathode, spectrum peak shifted to low energy compared with that near the anode. This result showed that a large amount of low energy electrons was generated on the surface of the FRP insulator near the cathode.

Journal Articles

Electrons in the negative-ion-based NBI on JT-60U

Kisaki, Masashi; Hanada, Masaya; Kamada, Masaki; Tanaka, Yutaka; Kobayashi, Kaoru; Sasao, Mamiko*

AIP Conference Proceedings 1097, p.344 - 352, 2009/03

The stripped electron trajectories in a large negative ion accelerator with multi-apertures and three acceleration stages, where non-uniform stray magnetic field is horizontally created, are calculated in the JT-60 negative ion source by the 3-D numerical code. The horizontal non-uniform stray field results in a significant power loss of the stripped electrons in the outmost acceleration channel on the grounded grid (GRG). The power loss in the outmost acceleration channel is more than twice higher than that in the central channel due to the weaker stray field although the total power loading on the GRG is by 25% larger than that by assuming a uniform stray field.

Oral presentation

Behavior of the electrons in the negative-ion-based-NBI source on JT-60U

Kisaki, Masashi; Hanada, Masaya; Kamada, Masaki; Tanaka, Yutaka; Sasao, Mamiko*

no journal, , 

no abstracts in English

Oral presentation

Improvement of voltage holding capability of negative ion source in JT-60U

Tanaka, Yutaka; Hanada, Masaya; Kobayashi, Kaoru; Akino, Noboru; Tanai, Yutaka*; Kisaki, Masashi

no journal, , 

no abstracts in English

Oral presentation

High energy beam profile diagnostics by using a negative ion probe beam, 2

Shinto, Katsuhiro; Wada, Motoi*; Nishida, Tomoaki*; Demura, Yasuhiro*; Sasaki, Daichi*; Tsumori, Katsuyoshi*; Kisaki, Masashi*; Nishiura, Masaki*; Kaneko, Osamu*; Sasao, Mamiko*

no journal, , 

no abstracts in English

Oral presentation

Development of a beam profile monitor using a negative ion probe beam for high intensity positive ion beams

Shinto, Katsuhiro; Wada, Motoi*; Nishida, Tomoaki*; Kisaki, Masashi*; Tsumori, Katsuyoshi*; Nishiura, Masaki*; Kaneko, Osamu*; Sasao, Mamiko*

no journal, , 

We have proposed a negative ion beam probe system as a new scheme to diagnose beam profiles of high power positive ion beams. We show the present status of the proof-of-principle experiment for the negative ion beam probe system performed at NIFS NBI test stand. A negative hydrogen ion source which produces a rectangular shape beam was installed at the diagnostic chamber in the NBI test stand and the total current of H$$^-$$ beam extracted from the ion source was measured. We obtained the total H$$^-$$ beam current of 10 $$mu$$A with the beam energy of 3 kV.

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