W7-AS: One step of the Wendelstein stellarator line

This paper is a summary of some of the major results from the Wendelstein 7-AS stellarator (W7-AS). W7-AS [G. Grieger et al., Phys. Fluids B 4, 2081 (1992)] has demonstrated the feasibility of modular coils and has pioneered the island divertor and the modeling of its three-dimensional characteristics with the EMC3/EIRENE code [Y. Feng, F. Sardei et al., Plasma Phys. Controlled Fusion 44, 611 (2002)]. It has extended the operational range to high density (4×1020m−3 at 2.5T) and high ⟨β⟩ (3.4% at 0.9T); it has demonstrated successfully the application of electron cyclotron resonance heating (ECRH) beyond cutoff via electron Bernstein wave heating, and it has utilized the toroidal variation of the magnetic field strength for ion cyclotron resonance frequency beach-wave heating. In preparation of W7-X [J. Nuhrenberg et al., Trans. Fusion Technol. 27, 71 (1995)], aspects of the optimization concept of the magnetic design have been successfully tested. W7-AS has accessed the H-mode, the first time in a “non-to...

[1]  L. Giannone,et al.  Physics optimization of stellarators , 1992 .

[2]  A. Werner,et al.  Survey of Magnetohydrodynamic Instabilities in the Advanced Stellarator Wendelstein 7-AS , 2001 .

[3]  A. Portas,et al.  Confinement and stability on the TJ-II stellarator , 2002 .

[4]  Manfred Thumm,et al.  Status of WENDELSTEIN 7-X construction , 2003 .

[5]  Carolin Schwab,et al.  Ideal magnetohydrodynamics: Global mode analysis of three‐dimensional plasma configurations , 1993 .

[6]  H. P. Laqua,et al.  BXO mode-converted electron Bernstein emission diagnostic (invited) , 2003 .

[7]  J. Snipes,et al.  Experimental and theoretical study of quasicoherent fluctuations in enhanced D(alpha) plasmas in the Alcator C-Mod tokamak. , 2002, Physical review letters.

[8]  Jeff M. Candy,et al.  Smoothness of turbulent transport across a minimum-q surface , 2004 .

[9]  F. Sardei,et al.  Influence of magnetic field configurations on divertor plasma parameters in the W7-AS stellarator , 2003 .

[10]  L. Spitzer.  The Stellarator Concept , 1958, IEEE Transactions on Plasma Science.

[11]  Experimental studies of electron transport , 2001 .

[12]  Tadashi Sekiguchi,et al.  Plasma Physics and Controlled Nuclear Fusion Research , 1987 .

[13]  Wagner,et al.  Experimental study of the principles governing tokamak transport. , 1986, Physical review letters.

[14]  Koji Takahashi,et al.  Observation of H-Mode Operation Windows for ECH Plasmas in Heliotron J , 2004 .

[15]  Ulrich Stroth,et al.  Evidence for convective inward particle transport in a stellarator , 1999 .

[16]  R. A. Dory,et al.  SPECIAL TOPIC: Energy confinement scaling from the international stellarator database , 1995 .

[17]  Spong,et al.  Neutral beam driven global Alfvén eigenmodes in the Wendelstein W7-AS stellarator. , 1994, Physical review letters.

[18]  A. Werner,et al.  Changes in density fluctuations associated with confinement transitions close to a rational edge rotational transform in the W7-AS stellarator , 2002 .

[19]  Y. Wang,et al.  H mode confinement in Alcator C-Mod , 1997 .

[20]  Matthias Hirsch,et al.  Impurity Transport Studies in the Wendelstein 7-AS Stellarator , 2004 .

[21]  E. D. Fredrickson,et al.  Experiments close to the beta-limit in W7-AS , 2003 .

[22]  ECRH-Group,et al.  Resonant and Nonresonant Electron Cyclotron Heating at Densities above the Plasma Cutoff by O-X-B Mode Conversion at the W7-As Stellarator , 1997 .

[23]  S. Zoletnik,et al.  Electric Field and Transport in W7-AS , 1999 .

[24]  D. Palumbo.  Some considerations on closed configurations of magnetohydrostatic equilibrium , 1968 .

[25]  J. Kisslinger,et al.  Viscous Damping of Rotation in Wendelstein 7-AS , 2000 .

[26]  F. Sardei,et al.  The divertor program in stellarators , 2002 .

[27]  Georg Kühner,et al.  High-confinement NBI discharges in the W7-AS stellarator , 1998 .

[28]  H. P. Laqua,et al.  20 years of ECRH at W7-A and W7-AS , 2003 .

[29]  L. Giannone,et al.  Optimized Confinement Discharges in the Stellarator W7-AS. , 2000 .

[30]  F. Wagner.  Importance of the divertor configuration for attaining the H-regime in ASDEX , 1984 .

[31]  L. Giannone,et al.  Characterization of the island divertor plasma of W7-AS stellarator in the deeply detached state with volume recombination , 2004 .

[32]  E. C. Crume,et al.  Plasma transport coefficients for nonsymmetric toroidal confinement systems , 1986 .

[33]  V. Erckmann,et al.  Current drive and bootstrap current in stellarators , 1992 .

[34]  Arkadi Kreter,et al.  Charge-Exchange Spectroscopy at the W7-AS Stellarator Employing a High-Energy Li Beam , 2003 .

[35]  P. T. Bonoli,et al.  First results from Alcator‐C‐MOD* , 1994 .

[36]  J. Nührenberg,et al.  Quasi-Helically Symmetric Toroidal Stellarators , 1988 .

[37]  D. Darrow,et al.  Energetic Ion Loss Diagnostic for the Wendelstein 7-AS Stellarator , 2001 .

[38]  Geist,et al.  H mode of the W 7-AS stellarator. , 1993, Physical review letters.

[39]  Itpa H-mode Power Threshold Databas Takizuka.  Roles of aspect ratio, absolute B and effective Z of the H-mode power threshold in tokamaks of the ITPA database , 2004 .

[40]  R. Brakel,et al.  Electron energy transport in the presence of rational surfaces in the Wendelstein 7-AS stellarator , 2002 .

[41]  G. Wolf,et al.  Burn condition, helium particle confinement and exhaust efficiency , 1990 .

[42]  M. Hirsch,et al.  Doppler reflectometry with optimized temporal resolution for the measurement of turbulence and its propagation velocity , 2004 .

[43]  P. Merkel,et al.  An integral equation technique for the exterior and interior Neumann problem in toroidal regions , 1986 .

[44]  F. Sardei,et al.  Transport in island divertors: physics, 3D modelling and comparison to first experiments on W7-AS* , 2002 .

[45]  K. Young.  The C-stellarator-a review of containment , 1974 .

[46]  Volker Dose,et al.  Dimensionally Exact Energy Confinement Scaling in W7-AS , 1998 .

[47]  A. Werner,et al.  Bolometer tomography at the density limit of the HDH mode in the W7-AS stellarator , 2003 .

[48]  K. Lackner,et al.  Tokamak Confinement in Relation to Plateau Scaling , 1990 .

[49]  Georg Kühner,et al.  Recent transport experiments in W7-AS on the stellarator-tokamak comparison , 1995 .

[50]  D. Eckhartt,et al.  Resistive Diffusion of Cesium Plasma in a Stellarator , 1966 .

[51]  Bill Scott,et al.  Doppler Reflectometry for the Investigation of Propagating Density Perturbations , 2001 .

[52]  Toshiyuki Iida,et al.  Multibody Fusion Model to Explain Experimental Results , 1995 .

[53]  Kozo Yamazaki,et al.  Configuration flexibility and extended regimes in Large Helical Device , 2001 .

[54]  U Wenzel,et al.  New advanced operational regime on the W7-AS stellarator. , 2002, Physical review letters.

[55]  Murakami,et al.  Bootstrap-current experiments in a toroidal plasma-confinement device. , 1991, Physical review letters.

[56]  P. Merkel,et al.  Three-dimensional free boundary calculations using a spectral Green's function method , 1986 .

[57]  Kozo Yamazaki,et al.  Recent advances in the LHD experiment , 2003 .

[58]  A. Hubbard,et al.  Studies of EDA H-Mode in Alcator C-Mod , 2000 .