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Journal Articles

High-beta steady-state research with integrated modeling in the JT-60 upgrade

Ozeki, Takahisa; JT-60 Team

Physics of Plasmas, 14(5), p.056114_1 - 056114_12, 2007/05

 Times Cited Count:4 Percentile:16.48(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Particle simulation of bursting Alfv$'e$n modes in JT-60U

Briguglio, S.*; Fogaccia, G.*; Vlad, G.*; Zonca, F.*; Shinohara, Koji; Ishikawa, Masao; Takechi, Manabu

Physics of Plasmas, 14(5), p.055904_1 - 055904_10, 2007/05

 Times Cited Count:41 Percentile:81.77(Physics, Fluids & Plasmas)

Journal Articles

Ultrarelativistic electron generation during the intense, ultrashort laser pulse interaction with clusters

Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Hayashi, Yukio; Homma, Takayuki; Inoue, Norihiro*; Kando, Masaki; Kanazawa, Shuhei; Kiriyama, Hiromitsu; Kondo, Shuji; et al.

Physics Letters A, 363(2-3), p.130 - 135, 2007/02

Collimated relativistic electrons up to 58 MeV with an electron charge of 2.1 nC were generated by the interaction of intense laser pulses with the Ar cluster target at the laser intensity of 3.5$$times$$10$$^{19}$$W/cm$$^{2}$$. The resulting spectrum does not fit a Maxwellian distribution, but is well described by a two-temperature Maxwellian, which indicates two mechanisms of the electron acceleration. Two dimensional particle-in-cell simulations demonstrate an important role of clusters. The higher energy electrons are injected when they are expelled from the clusters by the laser pulse field. They then gain their energy during the direct acceleration by the laser pulse, whose phase velocity in the underdense plasma is larger than speed of light in vacuum. The lower energy electrons, which are injected during the plasma wave breaking, are accelerated by the wakefield.

Oral presentation

Free boundary simulations of MHD instabilities with a finite volume based full-MHD code

Kagei, Yasuhiro; Kishimoto, Yasuaki; Miyoshi, Takahiro*; Takechi, Manabu

no journal, , 

no abstracts in English

Oral presentation

Online real time characterization of fast protons induced by a repetitive high-intensity laser-foil interaction

Yogo, Akifumi; Daido, Hiroyuki; Mori, Michiaki; Sagisaka, Akito; Ogura, Koichi; Orimo, Satoshi; Kiriyama, Hiromitsu; Pirozhkov, A. S.; Kanazawa, Shuhei; Nakai, Yoshiki; et al.

no journal, , 

We report the result on a novel online analysis of fast ions generated in an ultraintense laser-foil interaction. Fast protons are observed by a time-of-flight (TOF) detector, which is precisely calibrated using proton beams from an ion accelerator as to its detection efficiency depending on the proton energy. The TOF detector provides shot-to-shot energy distributions of protons immediately after the irradiation of a high-intensity laser pulse of 10$$^{18}$$ W/cm$$^2$$. Definite correlations are found between the prepulse intensity and the high energy cutoff of protons as well as the conversion efficiency of the laser energy into the proton energy, governing the stability of the repetitive proton generation.

Oral presentation

RWM analyses of JT-60SA and JT-60U tokamak plasmas

Kurita, Genichi; Bialek, J.*; Fujita, Takaaki; Tamai, Hiroshi; Matsukawa, Makoto; Matsunaga, Go; Takechi, Manabu; Tsuda, Takashi; Ozeki, Takahisa; Navratil, G. A.*; et al.

no journal, , 

JT-60SA is a tokamak device, being now designed at JAEA with collaboration of EU. One of the main purpose of JT-60SA is to realize the steady state plasma with high normallized beta values, 3.5$$sim$$5.5. Our previous analyses have shown that the critical normalized beta value was 3.8 with the effect of the stabilizing structure with finite resitivity and the active feedback control. The critical beta value is very low compared to the critical normalized beta of 5.5 in the case using ideal stabilizing structure, which results in very low C$$beta$$ value of 0.37 and bad efficiency of feedback control. To overcome these, we consider the new configuration of stabilizing structure and feedbacck control coil. The analyses are being carried out by VALEN code developed in Columbia University for new equiilibrium including transport analyses of JT-60SA plasma. We also present the results of analyses of experimental data of current driven and pressure driven RWM in JT-60U tokamak.

Oral presentation

Explosive growth and nonlinear dynamics of the forced magnetic island

Ishii, Yasutomo; Azumi, Masafumi; Smolyakov, A. I.*

no journal, , 

no abstracts in English

Oral presentation

Characteristics of turbulence dominated by zonal flows and large scale structures

Matsumoto, Taro; Kishimoto, Yasuaki*; Li, J.*

no journal, , 

In order to find rules to identify turbulent dynamics in tokamak plasmas, we studied the statistical characteristics from gyrofluid simulation for electron temperature gradient (ETG) turbulence in sheared slab configuration. The statistical characteristics such as fractal dimension, Lyapunov number, probability density function (PDF) are investigated in details for various turbulent structures dominated by intermittency, zonal flow, and nonlinearly excited tertiary waves. High dimensionality (d 8-10) and prominent exponential PDF tails are observed in turbulent plasmas, which exhibit an intermittent transport dynamics. The PDF tails are found to shows a prominent similarity insensitive to the plasma parameters such as temperature gradient and magnetic shear. On the other hand, in plasmas dominated by zonal flows and tertiary waves (Kelvin-Helmholtz), which is established in weak magnetic shear regime, a significant dimensionality lowering (up to d 3) is observed accompanied by disappearance of the exponential tails. The relation among different statistical values will be discussed.

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