Effects of ergodization on plasma confinement in JFT-2M

Shoji, T.; Tamai, Hiroshi; Miura, Y.; Mori, Masahiro; Ogawa, Hideyuki; Leonard, A. W.; Jensen, Thomas; Hyatt, A.W.; Howald, A. M.; Fuchs, Gerhard; Ohyabu, N.; Asakura, N.; Fujita, T.; Shimada, M.; Tsuji, S.; Maeda, Hideaki; Aikawa, Hiroshi; Hoshino, K.; Kasai, S.; Kawakami, T.; Kawashima, H.; Maeno, Masaki; Matsuda, Toshiaki; Ogawa, Toshihide; Seike, T.; Suzuki, Norio; Uehara, K.; Yamamoto, T.; Yamauchi, Toshihiko; Hamano, Tsuyoshi; Hasegawa, K.; Honda, A.; Kazawa, M.; Kashiwa, Y.; Kikuchi, Kenji; Okano, Haruo; Sato, Eiji; Seki, N.; Shibata, Takemasa; Shiina, T.; Suzuki, Satoshi; Tani, Tadaaki; Tokutake, T.; Tomiyama, Yoshiaki; Yamasato, T.

doi:10.1016/s0022-3115(06)80049-8

Cited by 38 publications

(23 citation statements)

References 4 publications

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“…Application of 3D fields can cause several effects that are of critical importance to future tokamaks such as ITER. ELMs are mitigated, suppressed, or triggered [5][6][7][8][9]. The pedestal profiles are affected, with some cases showing a flattening of the density and temperature profiles, while in others the pedestal pressure gradient increases.…”

Section: Introductionmentioning

confidence: 99%

Implementation of the 3D edge plasma code EMC3-EIRENE on NSTX

Lore¹,

Canik²,

Feng³

et al. 2012

Nucl. Fusion

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The 3D edge transport code EMC3-EIRENE has been applied for the first time to the NSTX spherical tokamak. A new disconnected double null grid has been developed to allow the simulation of plasma where the radial separation of the inner and outer separatrix is less than characteristic widths (e.g. heat flux width) at the midplane. Modeling results are presented for both an axisymmetric case and a case where 3D magnetic field is applied in an n=3 configuration. In the vacuum approximation the perturbed field consists of a wide region of destroyed flux surfaces and helical lobes which are a mixture of long and short connection length field lines formed by the separatrix manifolds. This structure is reflected in coupled 3D plasma fluid (EMC3) and kinetic neutral particle (EIRENE) simulations. The helical lobes extending inside of the unperturbed separatrix are filled in by hot plasma from the core. The intersection of the lobes with the divertor results in a striated flux footprint pattern on the target plates. Profiles of divertor heat and particle fluxes are compared to experimental data, and possible sources of discrepancy are discussed. IntroductionNon-axisymmetric fields affect both the transport and stability properties of tokamak plasmas. Even a small asymmetry in the ideal axisymmetric field, for example due to unavoidable field errors, can result in increased collisional transport [1], creation of magnetic islands [2], stochastic fields [3], and rotation damping [4]. 3D field structures are also generated intentionally by perturbing the plasma with control coils. Application of 3D fields can cause several effects that are of critical importance to future tokamaks such as ITER. ELMs are mitigated, suppressed, or triggered [5][6][7][8][9]. The pedestal profiles are affected, with some cases showing a flattening of the density and temperature profiles, while in others the pedestal pressure gradient increases. The heat and particle divertor loads are also affected, through strike point splitting [10][11][12] or changes in the divertor recycling properties, e.g., reattachment of the divertor plasma [13]. These effects can be seen as either detrimental behavior to be mitigated or as beneficial behavior to be exploited. With this viewpoint, the critical aspect is to have an understanding of the underlying physics so that reliable predictions can be made, and full advantage of potential benefits taken.Modeling of the above effects is complicated due to the 3D geometry and the coupling of parallel and cross-field transport. The opportunity exists, however, to apply to tokamaks advanced 3D codes originally developed for stellarator research. The EMC3-EIRENE code [14-16] is a coupled 3D Monte Carlo plasma fluid transport (EMC3) and kinetic neutral recycling and transport (EIRENE) package. The code includes transport of particles, electron and ion energy, and parallel momentum in stochastic fields with 3D plasma facing component geometries. EMC3-EIRENE has been applied to stellarators [15] and limiter tokamaks ...

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Section: Introductionmentioning

confidence: 99%

Implementation of the 3D edge plasma code EMC3-EIRENE on NSTX

Lore¹,

Canik²,

Feng³

et al. 2012

Nucl. Fusion

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“…[4][5][6][7][8][9]), in Tore Supra (Refs. [10][11][12][13][14][15][16][17]) and in a number of small-size tokamaks (in JFT-2M ( [18,19]), CSTN-II ( [20,21]), HYBTOK-II ( [22]), TBR-1 [23], TCABR ( [24]), and other small fusion devices ( [25,26]).…”

Section: Introductionmentioning

confidence: 99%

Modelling of magnetic field structure of the Ergodic Divertor of Tore Supra and comparison to the Dynamic Ergodic Divertor of TEXTOR

Abdullaev,

Van Rompuy,

Finken

et al. 2008

Preprint

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An analytical model previously developed to study the structure of the magnetic field for the TEXTOR-DED [S.S. Abdullaev et al. Phys. Plasmas, 6, 153 (1999)] is applied to the similar study of the Ergodic Divertor of Tore Supra tokamak [Ph. Ghendrih, Plasma Phys. Control. Fusion, 38, 1653(1996]. The coil configuration of ED Tore Supra consists of six modules equidistantly located along the toroidal direction on the low-field-side of the torus with given toroidal and poloidal extensions. The Hamiltonian formulation of field line equations in straight-field-line coordinates (Boozer coordinates) and the computationally efficient mapping method for integration of the Hamiltonian field line equations are used to study the magnetic field structure in the ED. Asymptotical formulas for the perturbation magnetic field created by the ED coils are obtained and the spectrum of magnetic perturbations is analyzed and compared with the one of the TEXTOR-DED. The structure of ergodic and laminar zones are studied by plotting Poincaré sections, so-called laminar plots (contour plots of wall to wall connection lengths) and magnetic footprints. The radial profiles of field line diffusion coefficients are calculated for different perturbation currents and it is found that for the Tore Supra case in the ergodic zone the numerical field line diffusion coefficients perfectly follow the quasilinear formula for smaller perturbation currents although the situation is different for the maximum perturbation current.

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“…Substituting equation (34) into equation (14), and taking account of the terms in equations (36)- (39), the jumps of the scalar potential derivatives, due to the surface current distribution, are ∂φ ∂r…”

Section: Appendix Magnetic Field Generated By An Ergodic Limiter Witmentioning

confidence: 99%

“…Finally, while the edge plasma potential was observed to change significantly in TEXT, which sometimes vanished or even changed its signal [15], in CSTN-II [16] the measured potential profile was observed to follow a pattern similar to the magnetic field lines along the poloidal plane. By applying resonant magnetic perturbations in JFT-2M, a steady H-mode plasma [34] and an improvement of the tokamak density limit [18] were achieved.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field structure in the TCABR tokamak due to ergodic limiters with a non-uniform current distribution: theoretical and experimental results

Pires

Saettone-Olschewski

Kucinski

et al. 2005

Plasma Phys. Control. Fusion

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The ergodic magnetic limiter is a device designed to generate a cold boundary layer of chaotic magnetic field lines at the peripheral region of a tokamak, with the main purpose of reducing the deleterious effects of the plasma-wall interaction. In the TCABR tokamak an ergodic limiter was constructed and recently installed inside the vacuum chamber. We developed a theoretical model for the action of an ergodic magnetic limiter in a large aspect-ratio tokamak taking into account the finite width of the limiter. The theoretical results are in good agreement with measurements of the vacuum magnetic field created by the limiter. Poincaré maps of field line flow are computed to reveal the resulting magnetic field line structure due to the ergodic limiter and show that the operation of the ergodic limiter in the TCABR tokamak is feasible and results in a chaotic boundary layer for limiter currents of about 6% of the plasma current.

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Effects of ergodization on plasma confinement in JFT-2M

Cited by 38 publications

References 4 publications

Implementation of the 3D edge plasma code EMC3-EIRENE on NSTX

Implementation of the 3D edge plasma code EMC3-EIRENE on NSTX

Modelling of magnetic field structure of the Ergodic Divertor of Tore Supra and comparison to the Dynamic Ergodic Divertor of TEXTOR

Magnetic field structure in the TCABR tokamak due to ergodic limiters with a non-uniform current distribution: theoretical and experimental results

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