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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:7 Percentile:56.83(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:100

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

Dynamics of ion internal transport barrier in LHD heliotron and JT-60U tokamak plasmas

Ida, Katsumi*; Sakamoto, Yoshiteru; Yoshinuma, Mikiro*; Takenaga, Hidenobu; Nagaoka, Kenichi*; Hayashi, Nobuhiko; Oyama, Naoyuki; Osakabe, Masaki*; Yokoyama, Masayuki*; Funaba, Hisamichi*; et al.

Nuclear Fusion, 49(9), p.095024_1 - 095024_9, 2009/09

 Times Cited Count:26 Percentile:26.42(Physics, Fluids & Plasmas)

Dynamics of ion internal transport barrier (ITB) formation and impurity transport both in the Large Helical Device (LHD) heliotron and JT-60U tokamak are described. Significant differences between heliotron and tokamak plasmas are observed. The location of the ITB moves outward during the ITB formation regardless of the sign of magnetic shear in JT-60U and the ITB becomes more localized in the plasma with negative magnetic shear. In LHD, the low Te/Ti ratio ($$<$$ 1) of the target plasma for the high power heating is found to be necessary condition to achieve the ITB plasma and the ITB location tends to expand outward or inward depending on the condition of the target plasmas. Associated with the formation of ITB, the carbon density tends to be peaked due to inward convection in JT-60U, while the carbon density becomes hollow due to outward convection in LHD. The outward convection observed in LHD contradicts the prediction by neoclassical theory.

Journal Articles

Spectroscopic observations of beam and source plasma light and testing Cs-deposition monitor in the large area negative ion source for LHD-NBI

Oka, Yoshihide*; Tsumori, Katsuyoshi*; Ikeda, Katsunori*; Kaneko, Osamu*; Nagaoka, Kenichi*; Osakabe, Masaki*; Takeiri, Yasuhiko*; Asano, Eiji*; Komada, Seiji*; Kondo, Tomoki*; et al.

Review of Scientific Instruments, 79(2), p.02C105_1 - 02C105_4, 2008/02

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

In the present studies, we studied the cesium lines in the source plasma during beam shots on the LND MN-NBI system. It was found for the first time in the LHD-source 2, that both the amount of Cs I (neutral Cs) and Cs II (Cs$$^{+}$$) in the source plasma light rose sharply when beam acceleration began, and continued rising during a 10 s pulse. We think that this was because the cesium was evaporated/sputtered from the source backplate by the back-streaming positive ions.

Journal Articles

Heating and current drive by N-NBI in JT-60U and LHD

Kaneko, Osamu*; Yamamoto, Takumi; Akiba, Masato; Hanada, Masaya; Ikeda, Katsunori*; Inoue, Takashi; Nagaoka, Kenichi*; Oka, Yoshihide*; Osakabe, Masaki*; Takeiri, Yasuhiko*; et al.

Fusion Science and Technology, 44(2), p.503 - 507, 2003/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

High energy negative-ion-based neutral beam injection (N-NBI) is expected as an efficient and reliable tool of heating and current driving for reactor plasmas such as ITER. A world wide activity on developing technology of negative ion production and beam formation started in 1980ユs and the great progress has been achieved up to now. In particular, Japan has two large projects that planned adopting N-NBI for real plasma experiments; the JT-60U tokamak and the LHD heliotron, which further motivated the R&D activity. These R&D programs were carried out at JAERI and NIFS separately in Japan, and both were successfully done. The first beam injection experiment was made on the JT-60U in 1996, followed by the LHD in 1998. They were the first experiments on heating plasma by high energy beam in tokamaks and in stellerators, and the obtained results were very promising.

Oral presentation

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

Shinto, Katsuhiro; Wada, Motoi*; Imakita, Shinsuke*; Kaneko, Osamu*; Tsumori, Katsuyoshi*

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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