Stability of a toroidal plasma by hot electron annulus in a bumpy torus

The ballooning instability is analyzed in a bumpy configuration using a relatively simple fluid model of an inhomogeneous slab plasma with gravitational field simulating the bad curvature effect and the grad-B effect due to hot electron annulus. Mathieu type equation is derived to investigate a linear analysis. Stability boundary giving the maximum stable Beta sub p (beta value of bulk plasma) as a function of Beta sub h and the threshold for Beta sub h (beta value of hot electron annulus) are studied for Nagoya bumpy torus parameters. The relevance of our theoretical analysis is discussed in a comparison with the previous results.