Equilibrium and Stability of High-{beta} Plasmas in Wendelstein 7-AS

Journal Article · Thu Jul 15 04:00:00 EDT 2004 · Fusion Science and Technology

OSTI ID:20849715

Geiger, Joachim E ^[1]; Weller, Arthur ^[1]; Zarnstorff, Michael C ^[2]; Nuehrenberg, Carolin ^[1]; Werner, Andreas Horst Franz ^[1]; Kolesnichenko, Yaroslav I ^[3]

---

1. Max-Planck-Institut fuer Plasmaphysik (Germany)
2. Princeton Plasma Physics Laboratory (United States)
3. Institute for Nuclear Research (Russian Federation)

One of the major goals for Wendelstein 7-AS (W7-AS) was the testing of the theoretical basis for the optimized configuration of Wendelstein 7-X (W7-X), currently under construction in Greifswald, Germany. In the last experimental campaign of W7-AS, volume-averaged {beta} values >3% have been achieved. The underlying experimental changes leading to these results are briefly reviewed. The equilibrium characteristics expected from magnetohydrodynamic (MHD) theory are modeled in a simplified picture and compared with three-dimensional equilibrium calculations. A wide range of parameters has been covered in the experiments with and without net toroidal currents. Experimental data are compared with free-boundary equilibrium calculations and exhibit good agreement. The high-{beta} equilibria usually showed only small MHD activity. The most prominent activities are low-frequency pressure-driven modes connected with low-order rationals also expected from numerical calculations using the CAS3D code, and Alfv and eacute;n modes driven by energetic particles from the tangential neutral beam injection. Comparison of experimentally measured frequencies and mode structures from soft-X-ray tomography with theoretical predictions also shows the improving understanding of these modes in stellarators. The agreement of experiment and theory gives confidence in the predictions for W7-X.

• OSTI ID: 20849715
• Journal Information: Fusion Science and Technology, Journal Name: Fusion Science and Technology Journal Issue: 1 Vol. 46; ISSN 1536-1055
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COMPARATIVE EVALUATIONS
ELECTRIC CURRENTS
EQUILIBRIUM
HIGH-BETA PLASMA
MAGNETOHYDRODYNAMICS
NEUTRAL ATOM BEAM INJECTION
SOFT X RADIATION
STABILITY
TESTING
THREE-DIMENSIONAL CALCULATIONS
TOMOGRAPHY
WENDELSTEIN-7 STELLARATOR