Plasma transport simulation modelling for helical confinement systems

Yamazaki, K.; Amano, Tsuneo

doi:10.1088/0029-5515/32/4/i08

Cited by 56 publications

(54 citation statements)

References 25 publications

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“…The measured radial electric field is compared with that predicted by neoclassical theory. The radial electric field E r is calculated with the balance of neoclassical ion flux and electron flux using the measured electron density, electron temperature, and ion temperature profiles [15]. The E r calculated with neoclassical theory in the electron root becomes larger towards the plasma edge as shown in Fig.…”

mentioning

confidence: 99%

Reduction of Ion Thermal Diffusivity Associated with the Transition of the Radial Electric Field in Neutral-Beam-Heated Plasmas in the Large Helical Device

Ida¹,

Funaba²,

Kado³

et al. 2001

Phys. Rev. Lett.

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Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss. Neoclassical ion transport is important in stellarator plasmas, because the helical ripple losses are comparable to or sometimes even higher than the anomalous losses in contrast to those in tokamaks. The crucial issues of neoclassical ion transport are (1) the reduction of ion thermal diffusivity due to a large positive radial electric field in the electron root [1][2][3], and (2) the reduction of ion thermal diffusivity due to the optimization of the magnetic field structure (s optimization) [3][4][5][6]. However, there has been no experimental study to test these issues on the neoclassical ion transport in stellarator plasmas. This is because the transition of the radial electric field from small negative (ion root) to large positive (electron root) was observed only in plasmas with the assistance of electron cyclotron heating (ECH), where electron heating is dominant [7][8][9][10][11]. The ion temperature is much lower than the electron temperature because ions are heated only by the energy exchange between ions and electrons. In these experiments, the significant increase of electron temperature and a clear reduction of electron thermal diffusivity were observed in the plasma core in the electron root. However, no reduction of ion thermal diffusivity was observed because of the lack of direct ion heating. There have been no experimental results to show the improvement of ion transport in the electron root, although a significant improvement of ion transport (rather than the electron transport) is predicted by the neoclassical theory [6]. This paper describes the experimental results of the neoclassical feature of ion transport for the first time, the reduction of ion thermal diffusivity due to the transition to the large positive electric field (electron root), and/or the optimization of the magnetic field structure (s optimization).The large helical device (LHD) [12] is a Heliotron device (poloidal period number L 2, and toroidal period number M 10) with a major radius of R ax 3.5 4.1 m, an average minor radius of 0.6 m, and magnetic field up to 3 T. The radial electric field ͑E r ͒ is derived from the poloidal and toroidal rotation velocity and pressure gradient of neon impurity measured with charge exchange spectroscopy [13] at the midplane in LHD (vertically elongated cross section) using a radial force balance. The radial force balance equation can be expressed as E r ͑en I Z I ͒ 21 ͑≠p I ͞≠r͒ 2 ͑y u B f 2 y f B u ͒, where B f and B u are toroidal a...

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confidence: 99%

Reduction of Ion Thermal Diffusivity Associated with the Transition of the Radial Electric Field in Neutral-Beam-Heated Plasmas in the Large Helical Device

Ida¹,

Funaba²,

Kado³

et al. 2001

Phys. Rev. Lett.

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“…In this study we conducted time-evolution analysis of the current density profile of burning tokamak plasmas by using 2-dimensional equilibrium, 1-dimensional transport code (TOTAL code [1]). The flowchart of this code is shown in Fig.…”

Section: Analysis Methodsmentioning

confidence: 99%

Current Profile Control for High Bootstrap Current Operation in ITER

Mano

Yamazaki

Oishi

et al. 2012

Plasma and Fusion Research

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For the achievement of steady-state fusion power plant, non-inductively current-driven plasma operation should be maintained in tokamak fusion reactors. Total non-inductive current is a summation of bootstrap current proportional to the plasma pressure gradient and externally driven non-inductive current such as neutral beam driven current. Especially in order to establish a commercial reactor, it is necessary to reduce the amount of external current-drive power and to maintain the majority of the plasma current with bootstrap current. Burning plasma has high autonomy, so the change in current density profile including changes in particle and heat transports should be checked. In this study time-evolution analysis of the current density profile for burning plasmas in the ITER machine has been conducted by using 2.0-dimensional equilibrium, 1.5-dimensional-transport code (TOTAL code). Here current-diffusive ballooning mode model was adopted as a heat transport model. It is concluded that external current-drive is required both in the center and near the periphery of the plasma in order to maintain steady-state profiles of temperature and density with high bootstrap current fraction.

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“…3 is caused by change in the heating power. The cause of positive temperature dependence of sawtooth periods by condition (5) in Fig. 3 is also investigated.…”

Section: Variations Of the Sawtooth Periods In Dt Plasmamentioning

confidence: 99%

“…The sawtooth periods in ITER are analyzed by using a 1.5-dimensional (1.5-D) transport code TOTAL (toroidal transport analysis linkage) [5]. The Porcelli model [6] has been newly implemented to the code to study the effects of fast particles and the magnetic shear on the sawtooth crashes.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Sawtooth Oscillation in Burning Plasma

Natsume

Fujita

Arimoto

et al. 2014

Plasma and Fusion Research

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The sawtooth oscillation is one of the important instabilities driven by the plasma current in tokamak plasma. The sawtooth period is a key parameter that characterizes the effect of the sawtooth oscillation on the plasma behavior. For prediction of sawteeth in burning plasma, the sawtooth model in the 1.5-dimensional transport code TOTAL has been extended to include the effects of fast particles and the magnetic shear. By using the newly implemented model, we simulated sawteeth in the presence of the alpha particles as the fast ion in ITER. It is found that the sawtooth periods in DT plasma are longer than those in DD plasma. In DT plasma, the sawtooth period doesn't change monotonically but has a peak as a function of the average central ion temperature or the RF heating power. This is because the mechanisms of triggering sawteeth are different in the low RF heating power region and in the high RF heating power region.

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Plasma transport simulation modelling for helical confinement systems

Cited by 56 publications

References 25 publications

Reduction of Ion Thermal Diffusivity Associated with the Transition of the Radial Electric Field in Neutral-Beam-Heated Plasmas in the Large Helical Device

Reduction of Ion Thermal Diffusivity Associated with the Transition of the Radial Electric Field in Neutral-Beam-Heated Plasmas in the Large Helical Device

Current Profile Control for High Bootstrap Current Operation in ITER

Simulation of Sawtooth Oscillation in Burning Plasma

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