A fully synthetic type-I ELM cycle diagnostic using conventional O-mode reflectometry.

Significant advances in modeling and simulations for microwave reflectometry have been conducted in recent years. An example is the integration of improved numerical descriptions of magneto-hydrodynamics (MHD) instabilities, obtained from MHD codes, together with 2D full-wave codes to implement synthetic reflectometry diagnostics in realistic conditions. In particular, the nonlinear MHD code JOREK has been used previously together with the 2D full-wave code REFMUL, to assess the response of conventional O-mode reflectometry along a Type-I edge localized mode (ELM) crash. In this work, a similar framework and synthetic diagnostic set-up are considered but with an extended MHD simulation where a Type-I ELM cycle comprised of several ELM crashes is studied. This includes the self-consistent MHD evolution along inter-ELM periods, which was absent in the previous study. The reflectometer response at the mid-plane of the low magnetic field side is used to provide information about the behavior of density fluctuations along the full ELM cycle. The inter-ELM periods display density fluctuations in agreement with the ELM triggering mechanisms manifesting as reflectometry signatures which are identified with ELM precursors. The precursor signatures are observed a few milliseconds before a transition from linear to non-linear reflectometry regimes occurs, associated with the explosive onset of the ELM. [ABSTRACT FROM AUTHOR]