STABILITY OF BOOTSTRAP CURRENT-DRIVEN MAGNETIC ISLANDS IN STELLARATORS

The stability of magnetic island producing perturbations due to fluctu ations in the bootstrap current in stellarator configuration is examin ed. The stability criterion depends on the sign of the derivative of t he rotational transform, the pressure gradient, and the direction of t he equilibrium bootstrap current, which is determined by the structure of Absolute value of B. It is found that quasihelically symmetric ste llarator configurations with p'/iota < 0 are unstable to the formation of bootstrap current-driven magnetic islands. The stability of conven tional stellarator configurations depends upon the field structure.