Extending the GRAY beam-tracer beyond the standard electron cyclotron heating modelling

Electron Cyclotron (EC) waves are playing an increasingly important role in the operation of next-generation fusion devices: Electron Cyclotron Resonant Heating (ECRH), will be the main plasma heating mechanism, and Electron Cyclotron Current Drive (ECCD) will be fundamental in controlling instabilities like sawteeth and Neoclassical Tearing Modes (NTM); in superconducting devices, EC waves are also becoming an essential tool to assist the ohmic breakdown in the start-up phase; finally, the interaction between EC waves and runaway electrons is being investigated as a new promising channel for exploring runaway dynamics. GRAY is a well-established beam-tracing code and a valuable tool for modeling EC waves, whose use has so far been mostly limited to predictive modeling of standard ECRH scenarios. More recently, efforts have been made to extend the applicability of GRAY across several additional fronts. We have designed and implemented robust algorithms for processing the inputs and improved the reliability of the simulation to enable realtime applications. The wave absorption model has been extended to also cover the conditions relevant for studying runaways-driven instabilities (n∥>1, high-energy anisotropic distribution). A new method, exploiting the algebraic properties of the dielectric tensor, has been developed to simultaneously compute all roots of the relativistic dispersion relation, including Electron Bernstein Waves (EBW). This solves numerical stability issues of the standard method and also enables the detection of mode conversion events, potentially unlocking new applications such as giving a first-order estimation of the conversion efficiency in the O-X-B heating scheme.