Magnetohydrodynamic stability of spheromak plasma in toroidal flux conserver with rectangular cross section

The stability of axially symmetric force-free equilibrium plasma is investigated. As a model of the flux conserver, a toroidal vessel with a rectangular cross section is considered. The radii of the inner and the outer walls of the vessel are denoted by R1 and R, and the height h. The plasma is shown to be stable for the ideal magnetohydrodynamic perturbations when h/R<(h/R)*, and unstable when R1/R<0.11 and (h/R)*<(h/R)<(h/R)+. The values of the critical ratios (h/R)* and (h/R)+ are evaluated as a function of R1/R. (author)