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Kojima, Atsushi; Kamiya, Kensaku; Fujita, Takaaki; Kubo, Hirotaka; Iguchi, Harukazu*; Oyama, Naoyuki; Suzuki, Takahiro; Kamada, Yutaka; JT-60 Team
Plasma and Fusion Research (Internet), 5, p.015_1 - 015_7, 2010/04
A lithium beam probe (LiBP) has been developed for the measurement of electron density profiles with high spatial and temporal resolutions in JT-60U. Using an electron beam heating ion source with a capability of 10 mA extraction, a 5.5 mA beam has been injected to the plasmas. Using the LiBP, time evolutions of pedestal density profiles during type I and grassy edge localized modes (ELMs) have been obtained for the first time. After a type I ELM crash, the drop of the line-integrated density measured by an interferometer delays by 2 ms later than that of the pedestal density. Comparing the line-integrated density to the line integration of the edge density profile measured by the LiBP, it is found that the recovery from the type I ELM crash is correlated with the reduction of core plasma density. Compared with the type I ELM, grassy ELMs have smaller density crashes than that of type I ELMs, which is mainly derived from the narrower ELM affected area.
Kojima, Atsushi; Kamiya, Kensaku; Iguchi, Harukazu*; Fujita, Takaaki; Kakiuchi, Hideto*; Kamada, Yutaka
Review of Scientific Instruments, 79(9), p.093502_1 - 093502_5, 2008/00
Times Cited Count：10 Percentile：44.77(Instruments & Instrumentation)A high-brightness and low-divergence neutral lithium beam is obtained for a Zeeman polarimetry of edge plasmas on JT-60U. In order to achieve high-brightness and low divergence angle simultaneously, the beam optics is designed after detailed numerical simulation taking the space charge effects into account. The newly-developed ion gun is operated on a test stand which simulates the diagnostic arrangement on JT-60U. The ion beam current of 10 mA is successfully extracted from the electron beam heated ion source. A sodium vapor neutralizer neutralizes the collimated ion beam fully at the temperature of 300
C. The neutral lithium beam is transported for 6.5 m long from the neutralizer. The HWHM radius of 26 mm and the equivalent beam current of 3 mA with the beam divergence angle of 0.2 degree are obtained. Those parameters satisfy the requirements of the Zeeman polarimetry. Furthermore, a long pulse extraction with a current of 10 mA and duration of 50 seconds is attained.
Kojima, Atsushi; Kamiya, Kensaku; Iguchi, Harukazu*; Fujita, Takaaki; Kamada, Yutaka
Plasma and Fusion Research (Internet), 2, p.S1104_1 - S1104_4, 2007/11
A lithium ion gun is under construction for a lithium beam Zeeman polarimetry on JT-60U. The performance of the prototype ion gun has been estimated by the numerical simulation taking the space charge effects into account. The target values of the ion gun are the beam energy of 30 keV, the beam current of 10 mA and the beam divergence angle within 0.13 degrees. The low divergence is required for the geometry of the Zeeman polarimetry on JT-60U where the observation area is 6m away from the neutralizer. The simulation results show the beam loss of 50% caused by the clash to the electrode such as an cathode and the neutralizer. Moreover, the beam transport efficiency from the neutralizer to the observation area is low due to the broadening of the divergence angle. The total beam efficiency is about 5%. Extracted current profile affects the beam property and efficiency. The peaked profile achieves better efficiency than the hollow one. As a result, beam current of 1mA is obtained at the observation area by the simulation for the prototype ion gun.
Fujisawa, Akihide*; Ido, Takeshi*; Shimizu, Akihiro*; Okamura, Shoichi*; Matsuoka, Keisuke*; Iguchi, Harukazu*; Hamada, Yasuji*; Nakano, Haruhisa*; Oshima, Shinsuke*; Ito, Kimitaka*; et al.
Nuclear Fusion, 47(10), p.S718 - S726, 2007/10
Times Cited Count：100 Percentile：95.26(Physics, Fluids & Plasmas)Present status of experiments on zonal flows is overviewed. Innovative use of modern diagnostics has revealed the existence of zonal flows, their spatio-temporal characteristics, their relationship with turbulence, and their effects on confinement. Particularly a number of observations have been accumulated on the oscillatory branch of the zonal flow, dubbed as geodesic acoustic modes suggesting necessity of theories to give their proper description. Several new methods have elucidated the zonal flow generation processes from the turbulence. Further investigation of relationship between the zonal flows and confinement is strongly encouraged as cross-device activity.
Kojima, Atsushi; Kamiya, Kensaku; Iguchi, Harukazu*; Fujita, Takaaki; Kamada, Yutaka
no journal, ,
no abstracts in English
Fujita, Takaaki; Kamiya, Kensaku; Kojima, Atsushi; Iguchi, Harukazu*; Oyama, Naoyuki; Suzuki, Takahiro; Kamada, Yutaka
no journal, ,
no abstracts in English
Kojima, Atsushi; Kamiya, Kensaku; Kakiuchi, Hideto*; Iguchi, Harukazu*; Fujita, Takaaki; Kamada, Yutaka
no journal, ,
no abstracts in English
Fujita, Takaaki; Kamiya, Kensaku; Kojima, Atsushi; Iguchi, Harukazu*; Oyama, Naoyuki; Suzuki, Takahiro; Kamada, Yutaka
no journal, ,
no abstracts in English
Kojima, Atsushi; Kamiya, Kensaku; Oyama, Naoyuki; Fujita, Takaaki; Kubo, Hirotaka; Iguchi, Harukazu*; Suzuki, Takahiro; Kamada, Yutaka
no journal, ,
In order to understand the ELM physics, a lithium beam probe system is developed using an electron beam heating ion source. The beam optics are optimized so as to decrease the beam divergence angle using the numerical simulation taking the space charge effects into account. A beam extraction with a beam current of 10 mA during 50 seconds is successfully demonstrated by the lithium beam injector. Then the edge density profile is measured with high time resolution of 0.5 msec and high spatial resolution of 1 cm. Then the density collapse due to ELM crash is successfully observed for the first time in type I and grassy ELMs.
Fujita, Takaaki; Kamiya, Kensaku; Kojima, Atsushi; Kubo, Hirotaka; Iguchi, Harukazu*; Oyama, Naoyuki; Suzuki, Takahiro; Kamada, Yutaka
no journal, ,
no abstracts in English
