Physics Issues in the Design of Low Aspect-Ratio, High-Beta, Quasi-Axisymmetric Stellarators
Authors: M.C. Zarnstorff, L.A. Berry, A. Boozer, A. Brooks, W.A. Cooper, M. Drevlak, E. Fredrickson, G.-Y. Fu, R. Goldston, R. Hatcher, S. Hirshman, W. Houlberg, S. Hudson, M. Isaev, C. Kessel, L.-P. Ku, E. Lazarus, J. Lewandowski, Z. Lin, J. Lyon, R. Majeski, P. Merkel, M. Mikhailov, D. Mikkelsen, W. Miner, D. Monticello, H. Mynick, G.H. Neilson, B.E. Nelson, C. Nuehrenberg, N. Pomphrey, M. Redi, W. Reiersen, A. Reiman, P. Rutherford, R. Sanchez, J. Schmidt, D. Spong, S. Subbotin, P. Strand, D. Strickler, P. Valanju, and R.B. White
Date of PPPL Report: November 2000
Presented at: the 18th International Atomic Energy Agency's (IAEA) Fusion Energy Conference 2000 (FEC-2000) held in Sorrento, Italy, October 4-10, 2000. An unedited proceedings will be published by IAEA in electronic format (CD-ROM) only.
Compact stellarators have the potential to combine the best features of the stellarator and the advanced tokamak, offering steady state operation without current drive and potentially without disruptions at an aspect ratio similar to tokamaks. A quasi-axisymmetric stellarator is developed that is consistent with the boot-strap current and passively stable to the ballooning, kink, Mercier, vertical, and neoclassical tearing modes at b = 4.1 % without need for conducting walls or external feedback. The configuration has good flux surfaces and fast ion confinement. Thermal transport analysis indicates that the confinement should be similar to tokamaks of the same size, allowing access to the b-limit with moderate power. Coils have been designed to reproduce the physics properties. Initial analysis indicates the coils have considerable flexibility to manipulate the configuration properties. Simulations of the current evolution indicate the kink-mode can remain stable during the approach to high-beta.