Development and application of HINT2 to helical system plasmas

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Property of pressure driven modes in Large Helical Device (LHD) plasmas with a resonant magnetic perturbation (RMP) is numerically studied. Particularly, we analyze three-dimensional (3D) RMP effects on the linear magnetohydrodynamic (MHD) stability of the modes. For this purpose, 3D numerical codes are utilized for both calculations of an equilibrium including an RMP generating an m = 1/n = 1 magnetic island and the stability of the perturbations resonant at theί = 1 surface. Here, m and n are the poloidal and the toroidal mode numbers, respectively, andί denotes rotational transform. Owing to the RMP, the pressure driven mode is localized around the X-point of the island. The type of the mode structure changes from the interchange type to the ballooning type. This property is attributed to the fact that the equilibrium pressure gradient is larger at the X-point than at the O-point.

Section: D Lhd Equilibrium Including Rmpmentioning

confidence: 99%

“…For this purpose, we utilize the HINT2 [5] and the MIPS [6] codes for the equilibrium and the MHD stability calculations, respectively. The HINT2 code finds a 3D MHD equilibrium without an assumption of the existence of nested surfaces.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Numerical Analysis of Pressure Driven Mode in RMP-Imposed LHD Plasma

Ichiguchi

Suzuki

Sato

et al. 2014

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“…Up to now, three-dimensional (3D) magnetohydrodynamic (MHD) equilibria were studied using a 3D MHD calculation code, HINT/HINT2 [5,6], which is an initial value solver based on the relaxation method without the assumption of nested flux surfaces. In Refs.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Stochasticity on Transport Properties in High-β LHD

Suzuki

Watanabe

Funaba

et al. 2009

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Effects of the stochasticity of magnetic field lines on transport properties are investigated. In a high-β LHD plasma, the structure of field lines in the peripheral region becomes stochastic by finite-β effects but the finite pressure gradient exists in that region. The radial diffusion coefficient and the Kolmogorov length of stochastic field lines are estimated. In the stochastic region, the radial diffusion of stochastic field lines becomes large and the Kolmogorov length becomes short due to increasing β. In that region, the radial heat transport becomes large due to the stochasticity of field lines.

“…In particular, spontaneous annihilation of magnetic islands called 'self-healing' triggers the improvement of plasma confinements. Magnetic islands and stochastic layers in helical plasmas have been investigated in the context of the three-dimensional resistive magnetohydrodynamics (MHD) equilibrium [4], and mechanism of the self-healing is under investigation. Such bifurcation is also observed in tokamaks, and theoretical works reveal that poloidal and toroidal rotations of plasmas play key roles, screening the penetration of RMPs [5].…”

mentioning

confidence: 99%

Forced Magnetic Reconnection in Helical Plasmas

Nishimura

Narushima

Toda

et al. 2010

Magnetic islands excited by resonant magnetic perturbations (RMPs) in helical plasmas are investigated. A Rutherford-type equation is coupled with the time evolution equation of the radial electric field associated with the neoclassical particle diffusion due to helically rippled magnetic fields. Using the model, bifurcation between the excitation and the annihilation of non-rotating magnetic islands are newly observed, depending on the magnitude of RMPs and the anomalous plasma viscosity. It is found that the transition between these states is triggered by the change in the radial electric field profile in the vicinity of magnetic island. Keywords: magnetic island, radial electric field, plasma rotation, neoclassical particle diffusion DOI: 10.1585/pfr.5.040Forced magnetic reconnection due to resonant magnetic perturbations (RMPs) is of great interest in magnetic fusion plasmas. Bifurcation of equilibria between with and without magnetic islands is observed in helical devices such as the LHD [1, 2] and the TJ-II [3], where the tearing mode is linearly stable. In particular, spontaneous annihilation of magnetic islands called 'self-healing' triggers the improvement of plasma confinements. Magnetic islands and stochastic layers in helical plasmas have been investigated in the context of the three-dimensional resistive magnetohydrodynamics (MHD) equilibrium [4], and mechanism of the self-healing is under investigation. Such bifurcation is also observed in tokamaks, and theoretical works reveal that poloidal and toroidal rotations of plasmas play key roles, screening the penetration of RMPs [5]. In helical plasmas, the poloidal rotation is driven by E × B and diamagnetic drifts, where radial electric fields are produced by the neoclassical particle diffusion associated with helically rippled magnetic fields [6]. Therefore, the poloidal rotation might be associated with the self-healing mechanism. In order to test this hypothesis, theoretical models including finite Lamor radius (FLR) effects, such as the neoclassical particle diffusion, are necessary.In this paper, we introduce a simple theoretical model describing the forced magnetic reconnection in helical plasmas, and the bifurcation mechanism associated with the poloidal rotation is examined.The derivation of the model equations is outlined below. We start from two-fluids equations including FLR effects based on the drift ordering [7]. Perpendicular electric current is composed of the polarization current, the diamagnetic current and currents due to anisotropic presauthor's e-mail: nishimura.seiya@lhd.nifs.ac.jp sure tensors. Neoclassical particle fluxes are perturbatively included by substituting gyrophase-averaged distribution functions given by linearized drift-kinetic equations into moment formulae of anisotropic pressure tensors. We adopt a simplified version of the radial neoclassical particle fluxes given in Ref. [8]. For parallel electric currents, we focus on the regime where the bootstrap current is less important than the inductive current. In fact, ...