MULTIPLE EQUILIBRIA OF DIVERTOR PLASMAS

A one-dimensional, two-fluid transport model with a temperature-depend ent neutral recycling coefficient is shown to give rise to multiple eq uilibria of divertor plasmas (bifurcation). Numerical techniques for o btaining these multiple equilibria and for examining their stability a re presented. Although these numerical techniques have been well known to the scientific community, this is the first time they have been ap plied to divertor plasma modeling to show the existence of multiple eq uilibria as well as the stability of these solutions. Numerical and ap proximate analytical solutions,of the present one-dimensional transpor t model both indicate that there exists three steady-state solutions c orresponding to (1) a high-temperature, low-density equilibrium, (2) a low-temperature, high-density equilibrium, and (3) an intermediate-te mperature equilibrium. While both the low-temperature and the high-tem perature equilibria are stable, with respect to small perturbations in the plasma conditions, the intermediate-temperature equilibrium is ph ysically unstable, i.e., any small perturbation about this equilibrium will cause a transition toward either the high-temperature or low-tem perature equilibrium.