Bifurcation and relaxation oscillations in divertor plasmas

This paper presents a contribution to bifurcation phenomena in scrape-off layer modelling. The bifurcations are caused by the non-monotonic temperature behaviour of the radiation characteristics of plasma impurities. Low-frequency relaxation oscillations observed in divertor plasmas of the ASDEX Upgrade tokamak are analyzed and computed using a simple model for the dynamics of the impurity density and the electron temperature. The corresponding model equations are a special case of a general system of transport equations whose stability is analyzed. Bifurcations are calculated by solving autonomous and parametrically driven model equations.