PPPL-3977 is available in pdf format (780 KB).
Criteria for Second Stability for Ballooning Modes in Stellarators
Authors: S.R. Hudson and C.C.Hegna
Date of PPPL Report: July 2004
Published in: Phys. Plasmas 11:9 (September 2004) L53-L56.
An expression determining how variations in the pressure-gradient and average magnetic shear affect ballooning stability for a stellarator equilibrium is presented. The procedure for determining the marginal stability boundaries, for each field line, depends only on the equilibrium and a single ballooning eigenfunction calculation. This information is sufficient to determine if increasing pressure-gradient is stabilizing or destabilizing and to predict whether the configuration possess a second stable region.