Calculating RF current condensation with self-consistent ray-tracing

Abstract

By exploiting the nonlinear amplification of the power deposition of RF waves, current condensation promises new pathways to the stabilisation of magnetic islands. We present a numerical analysis of current condensation, coupling a geometrical optics treatment of wave propagation and damping to a thermal diffusion equation solver in the island. Taking into account the island geometry and relativistic damping, previous analytical theory can be made more precise and specific scenarios can be realistically predicted. With this more precise description, bifurcations and associated hysteresis effects could be obtained in an ITER-like scenario at realistic parameter values. Moreover, it is shown that dynamically varying the RF wave launching angles can lead to hysteresis and help to avoid the nonlinear shadowing effect. II. COUPLING OF RAY-TRACING AND MAGNETIC ISLAND MODELThe numerical approach presented below aims to simulate the nonlinear dynamics of current condensation, yielding selfconsistent temperature and power depositions. The newly developed code OCCAMI (Of Current Condensation Amid