Ballooning stability of tokamak, screw-pinch, and turbulently heated tokamak plasmas

The plasma ballooning stability of three sets of equilibria characteristic of tokamak, screw pinch, and turbulently heated tokamak has been investigated. Already at low beta, the tokamak becomes ballooning-unstable and enters at higher betas again a stable region when q on axis is larger than unity. The screw pinch remains stable up to high betas and no second stable region can be found. The third equilibrium is always Mercier-unstable in the centre of the plasma.