This article has an erratum: [https://doi.org/10.1051/epjconf/202327703012]
EPJ Web Conf.
Volume 277, 202321st Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating (EC21)
|Number of page(s)||6|
|Published online||23 February 2023|
Radial localization of electron temperature pedestal and ELM-like events using ECE measurements at Wendelstein 7-X
Max Planck Institute for Plasma Physics, Wendelsteinstrasse-1, 17489, Greifswald
2 Los Alamos National Laboratory, Los Alamos, NM, USA
* e-mail: firstname.lastname@example.org
** See Thomas Sunn Pedersen et al 2022 Nucl. Fusion 62 042022 for the W7-X Team
Published online: 23 February 2023
A magnetic configuration scan was performed at Wendelstein 7-X stellarator by varying the rotational transform to analyze the plasma confinement for magnetic configurations with different edge magnetic island locations and sizes. For the magnetic configurations, where the 5/5 island chain was moved inside the last closed flux surface, it was observed with electron cyclotron emission measurements that an electron temperature, Te, pedestal develops in the plasma buildup phase and followed by the edge localized mode (ELM)-like crashes. From the mapping of the island to the plasma radius from HINT equilibrium, it was found that the Te pedestal is formed at the island location on the high field side of the plasma. The ELM-like crashes occur at the location of the pedestal and the transport barrier is broken typically with an energy loss of 3-4% during a single ELM-like event. The frequency and the amplitude of the ELM-like crashes were observed to be changing with island size, plasma heating power and density. Additionally during the plasma decay, after the heating was switched-off, a transition to degraded plasma confinement state was observed with changed Te profile gradients, faster decay rate of diamagnetic energy, and increased H-alpha levels.
© The Authors, published by EDP Sciences, 2023
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