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. Fusion54 025009) and a new method based on the MARS-F MHD stability code (Liu et al 2000 Phys. Plasmas7 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.
Effect of negative triangularity on tearing mode stability in tokamak plasmas