Aspect ratio scaling of ideal no-wall stability limits in high bootstrap fraction tokamak plasmas

The plasma aspect ratio dependence of ideal no-wall magnetohydrodynamics stability limits in high bootstrap fraction regimes was analyzed. It was found that at low aspect ratio the scaling of normalized beta with internal inductance is strongly aspect ratio dependent. Plasma current scans at two aspect ratios show that there is no unique or near edge q-value which defines the current limit for limiter boundary shapes. It was also shown that the nonrotating plasma no-wall stability limit has been exceeded by as much as 30% in National Spherical Torus Experiment (NSTX) in a high bootstrap fraction regime.