MARFE formation in diverted tokamaks

Abstract

We consider the equilibrium and stability of Marfes. We demonstrate that important aspects of the 2-dimensional problem can be illustrated by a 1-dimensional treatment. A stability analysis indicates that Marfe formation requires low temperature, high impurity content and low cross field transport. Additionally, Marfes tend to form on flux surfaces that contain an x-point. We observe that the transition to a Marfe-like solution can result from a fluctuation-induced jump from a neighboring constant temperature solution.1

Marfes: a magnetohydrodynamic stability study of two-dimensional tokamak equilibria

“…The 'classical' marfe, i.e. a marfe inside the last closed magnetic surface, is studied, not the marfe observed more recently in divertor geometry [11][12][13][14]. For the calculations, we focused mainly on typical marfe shots in limiter operations such as JET shot #20336 (NBI heating, carbon tiles with beryllium evaporation) and JET shot #20844 (only ohmic heating, beryllium tiles).…”