Physics lssues in Long Pulse Plasma Confinement

Physics in the steady-state or long time discharge are illustrated from the view point of generic toroidal plasmas. Issues include physics process with very long time scale, dynamical phenomena of various time scales, transition nature under very slow temporal variations of parameters, statistical occurrence of transition and life time and identification of minimum circulating power. Nonlinear dependencies of transport properties of density, temperature, current, electric field and poloidal magnetic field cause self-organized dynamics. A picture of stationary oscillatory states is presented from a unified picture of nonlinear limit cycle dynamics. It is emphasized that the long time asymptotics are determined by the structure formation mechanisms. The sustainment needs a circulating power, and the circulating power in steady state plasma is also discussed. Keywords: stationary state, self-generated oscillations, bifurcation, density limit oscillation, thermo-electric oscillation, statistical excitation, circulating power 1. lntroduction Recently attentions are attracted to the study o