Confinement, Flow Damping and Flexibility of Quasi-Poloidal Stellarators
Abstract
Quasi-poloidal (QP) stellarators have achieved levels of optimization that significantly suppress neoclassical transport relative to anomalous levels. QP symmetry also allows poloidal flow damping to be less than toroidal flow damping. This ordering (reversed from that of tokamaks) should allow more efficient control of the radial electric field with less required momentum input. An analysis of flow dynamics in such systems has been initiated using viscosity coefficients that can be derived from the usual transport coefficients (density/energy diffusion, bootstrap current. resistivity enhancement). The dependencies of these coefficients on plasma parameters such as collisionality and electric field will be analyzed and implications for flow evolution discussed. By varying the modular and vertical field coil currents in proposed QP systems, substantial flexibility has been demonstrated theoretically with respect to neoclassical confinement, quasi-poloidal symmetry, flow damping, and magnetic island widths. Variations of a factor of 20 in low collisionality neoclassical transport rates and a factor of 5 in quasi poloidal symmetry can be achieved. Work supported by U.S. Department of Energy under Contract DE-AC05 00OR22725 with UT-Battelle, LLC.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..DPPRP1023S