Shigeru KONOSHIMA

Investigation of magnetic field ripple effects on charged particles transport in scrape-off layer of Heliotron J

Furui Cai, S. Kado, G. Kawamura, Yuhe Feng et autres

Abstract The impact of helical magnetic ripples on the transport of plasma and carbon impurities in the scrape-off layer (SOL) of a Heliotron J device was investigated using the EMC3-EIRENE code. Comparisons with a simplified one-dimensional fluid model revealed that the transport …

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Assessment of divertor structures arising from invariant features in Hamiltonian system for three-dimensional magnetic field in Heliotron J

Furui Cai, S. Kado, G. Kawamura, Yuhe Feng et autres

Abstract The divertor structures of Heliotron J were investigated by analyzing the three-dimensional magnetic field and plasma transport simulations. The magnetic field of Heliotron J typically exhibits a characteristic resonant structure, where the stable and unstable manifolds emanating from specific X-points determine …

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Development of systematic exploration of magnetic configurations in Heliotron J

F. Kin, Shinji KOBAYASHI, A. Matsuyama, Furui Cai et autres

Abstract We develop a systematic configuration-search methodology for the Heliotron J helical-axis heliotron, combining a Bayesian exploration approach with field-line tracing and evaluation of magnetic field structural parameters. The methodology enables efficient exploration of an enormous coil current parameter space ( ∼ …

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First Plasma Experiment of Electron Cyclotron Resonance Heating by Optical Vortex Beam in Heliotron J

Zongyuhui He, Kazunobu NAGASAKI, Toru TSUJIMURA, Yasuhisa Oda et autres

Plasma experiments on electron cyclotron resonance heating (ECRH) using a high-power optical vortex beam (OVB) have been demonstrated for the first time in the Heliotron J stellarator/heliotron device. The OVB is generated by a spiral phase plate in a 70 GHz ECRH …

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Investigation of low-frequency fluctuation modulating turbulence during L–H transition in Heliotron J

F. Kin, Yuya Kondo, MAKOTO SASAKI, Akira Miyashita et autres

In this study, we observed a distinct low-frequency (LF) fluctuation in the n/m = 4/9 configuration under electron cyclotron heating (ECH) and neutral beam injection heating—conditions favorable for the L–H transition in Heliotron J [Sano et al., Nucl. Fusion 45, 1557 (2005)]. …

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Effect of edge magnetic islands on poloidal flow in electron cyclotron heated Heliotron J Plasmas

Yuya Kondo, K. Nagasaki, S. Ohshima, Daisuke Kuwahara et autres

Abstract Magnetic islands are formed at the plasma edge in Heliotron J, a stellarator/heliotron device, by controlling the rotational transform, and the effect of the magnetic islands on the poloidal flow profile was investigated using a Q-band Doppler reflectometer. Comparative measurements were …

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Dynamics of plasma reconfiguration after pellet injection in Heliotron J

Kumi Ogihara, S. Inagaki, S. Kado, Ryo Matsutani et autres

Because of the many degrees of freedom in magnetized plasmas, the plasma is largely reconfigured when the plasma achieves a non-equilibrium steady state in response to changes in the internal environment. Here we report observations of a plasma reconfiguration process when the …

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Dynamics of plasma reconfiguration after pellet injection in Heliotron J

S. Inagaki, S. Kado, Ryo Matsutani, G. Motojima et autres

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High-sensitivity measurement of Zeeman effect using hydrogen Paschen-α emission line in fusion-divertor-relevant plasma

Minato Murakumo, T. Shikama, S. Kado, Akihiro Iwata et autres

In magnetically confined fusion reactors, the Zeeman effect can sometimes be utilized in spatially resolved spectroscopy to localize the observed line emission. To apply this method to divertor plasma spectroscopy, the relative magnitude of the Zeeman splitting to linewidth for hydrogen atomic …

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Measurement of x-ray bremsstrahlung radiation from high energy electrons by stochastic acceleration in Heliotron J

Ryo Yamato, Shinji KOBAYASHI, T. Fujita, Kenichi NAGAOKA et autres

A synthetic diagnostic of x-ray bremsstrahlung radiation and a Monte Carlo radiation transport simulation were carried out to obtain the electron energy distribution in stochastic acceleration experiments in Heliotron J, a mid-sized heliotron-type magnetic confinement device. Three sets of LaBr3(Ce) scintillator and …

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Transition from divertor to limiter configuration and associated transient plasma oscillation in Heliotron J

Akira Miyashita, S. Ohshima, Ze Ning Xu, F. Kin et autres

Abstract A transition from a divertor configuration to a limiter configuration and associated transient plasma oscillation were observed in configurations whose confinement region expanded with the codirected plasma current in the Heliotron J device. The transition was associated with the edge plasma …

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Author response for "Transition from divertor to limiter configuration and associated transient plasma oscillation in Heliotron J"

Akira Miyashita, S. Ohshima, Ze Ning Xu, F. Kin et autres