Recent Advances in the Design of Quasi-Axisymmetric Stellarator Plasma Configurations
Authors: A. Reiman, L. Ku, D. Monticello, S. Hirshman, S. Hudson, C. Kessel, E. Lazarus, D. Mikkelsen, M. Zarnstorff, L.A. Berry, A. Boozer, A. Brooks, W.A. Cooper, M. Drevlak, E. Fredrickson, G. Fu, R. Goldston, R. Hatcher, M. Isaev, C. Jun, S. Knowlton, J. Lewandowski, Z. Lin, J.F. Lyon, P. Merkel, M. Mikhailov, W. Miner, H. Mynick, G. Neilson, B.E. Nelson, C. Nührenberg, N. Pomphrey, M. Redi, W. Reiersen, P. Rutherford, R. Sanchez, J. Schmidt, D. Spong, D. Strickler, A. Subbotin, P. Valanju, and R. White
Date of PPPL Report: January 2001
Published in: Phys. Plasmas 8 (May 2001) 2083-2094.
Strategies for the improvement of quasi-axisymmetric stellarator configurations are explored. Calculations of equilibrium flux surfaces for candidate configurations are also presented. One optimization strategy is found to generate configurations with improved neoclassical confinement, simpler coils with lower current density, and improved flux surface quality relative to previous designs. The flux surface calculations find significant differences in the extent of islands and stochastic regions between candidate configurations. (These calculations do not incorporate the predicted beneficial effects of perturbed bootstrap currents.) A method is demonstrated for removing low-order islands from candidate configurations by relatively small modifications of the configuration. One configuration is identified as having particularly desirable properties for a proposed experiment.