Magnetohydrodynamic stability of non-ideally peeling-ballooning limited pedestals in JET
Time: Tue 2025-12-09 10.00
Location: F3, Lindstedtvägen 26
Video link: https://kth-se.zoom.us/j/61118773378
Language: English
Subject area: Electrical Engineering
Doctoral student: Hampus Nyström , Elektromagnetism och fusionsfysik
Opponent: Professor Dr. Elisabeth Wolfrum, Max-Planck-Institut für Plasmaphysik, Garching, Germany
Supervisor: Professor Lorenzo Frassinetti, Elektromagnetism och fusionsfysik; Professor Per R. Brunsell, Elektromagnetism och fusionsfysik
QC 20251110
Abstract
Fusion power is a promising candidate for providing large amounts of sustainable, planable power to complement other sustainable energy solutions in the future. The tokamak, which is the fusion device furthest along to achieving this goal, confines a hot plasma with the help of magnetic fields. The performance of the tokamak is highly dependent on the performance of a thin region near the plasma edge, called the pedestal. Accurate models for predicting the pedestal behavior is therefore paramount for the optimization of future fusion reactors. The pedestal height is typically limited by the onset of ideal magnetohydrodynamic (MHD) instabilities called edge localized modes (ELMs). In the JET tokamak, it has however been observed that sometimes the pre-ELM pedestal can sometimes be stable to ideal MHD modes.
This thesis investigates the physics which are required to reconcile modeling and experimental results in pedestals which are not marginally unstable to ideal MHD modes when the ELM is triggered. It is shown that a key component that seems to be missing is the lack of resistivity in the MHD modeling. To investigate the impact of resistivity on the MHD modeling, a resistive MHD code has been implemented into the MHD stability frameworks used at JET. Including the resistivity improves the agreement between model and experiment compared to ideal MHD. In particular, the impact of changing the main fuel isotope mass and the impurity content on the pedestal performance is captured when resistive MHD is used.