THERMAL-STABILITY OF THE TOKAMAK PLASMA EDGE

The general linear, fluid, thermal instability theory for the plasma e dge has been extended. An analysis of a two-dimensional fluid model of the plasma edge has identified the importance of many previously unap preciated phenomena associated with parallel and gyro-viscous forces i n the presence of large radial gradients, with large radial or paralle l flows, with the temperature dependence of transport coefficients, an d with the coupling of temperature, how and density perturbations. The radiative condensation effect is generalized to include a further des tabilizing condensation effect associated with radial heat conduction. Representative plasma edge neutral and impurity densities are found t o be capable of driving thermal instabilities in the edge transport ba rrier and radiative mantle, respectively.