Tearing stability in toroidal plasmas with shaped cross section

Two methods for calculating tearing mode stability are described in this paper. A fast method using the recently improved T7 code (Ham et al 2012 Plasma Phys. Control. Fusion 54 025009) and a new method based on the MARS-F MHD stability code (Liu et al 2000 Phys. Plasmas 7 3681) which constructs the tearing mode solution from calculated basis functions in the full geometry of the problem. The effects of plasma toroidicity and cross-sectional shaping on tearing mode stability are investigated using both of the methods; the resultant stabilizing effects are in reasonable agreement over the range of parameters investigated. The parameter-space explored includes JET-like and ITER-like plasma shaping. While T7 can be used for rapid calculations and parameter scans, the MARS-F construction technique produces the more accurate value of the tearing mode stability index.