Structure and Nonlinear Development of Edge Localized Modes on the Tokamak ASDEX Upgrade  

Edge localized modes (ELMs) are periodic instabilities that might cause intolerably high heat fluxes onto first wall materials in future fusion devices.

Edge localized modes (ELMs) are periodic bursty instabilities that occur close to the boundary of magnetically confined fusion plasmas. These ELM crashes release particles and stored energy on a millisecond time scale. Therefore, they might cause intolerably high heat fluxes onto first wall materials in future fusion devices. In order to predict the effect of ELMs, they have to be characterized and understood very accurately. One of the main characterizing parameters of the ELMs is their periodic magnetic structure given by the toroidal mode number n.

Toroidal mode number distribution measured during the nonlinear phase of ELM crashes in two ASDEX Upgrade discharges with different q95 values.

The development of these n numbers during the nonlinear phase of the ELM crash was now discovered with the help of magnetic pick-up coils for the first time on the tokamak ASDEX Upgrade. This enabled a quantitative comparison to potentially predictive theory, i.e. the nonlinear magnetohydrodynamics code JOREK. Furthermore, a scaling of n with the edge safety factor q95 being a measure for the inclination of the magnetic field lines was found. For this work Felician Mink received his doctorate from TUM on the 18th of April 2018.

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