Identification of a network of nonlinear interactions as a mechanism triggering the onset of edge localized modes. (27th July 2020)

• Record Type: Journal Article
• Authors: Dominski, J; Diallo, A
• Is Part Of: Plasma physics and controlled fusion. Volume 62:Number 9(2020)
• Publication Date: 2020-07-27
• Subjects: pedestal -- magnetic fluctuations -- non-linear dynamics; Plasma (Ionized gases) -- Periodicals; Controlled fusion -- Periodicals; 530.44
• DOI: 10.1088/1361-6587/ab9c48
• Languages: English
• ISSNs: 0741-3335

Abstract

Abstract: Edge localized modes (ELMs) remain a critical issue for the lifetime of in-vessel components of fusion reactors such as ITER. We study ELMs triggered when the pedestal parameters are below the peeling-ballooning limit. These ELMs occur while the pedestal recovers after an ELM crash. We identify a mechanism by which a non-linear perturbation involving many active triads—a network of non-linear interactions – leads to the triggering of these ELMs. Each active triad leads to the non-linear transfer of energy between three waves, such that the network of non-linear interactions lead to a transfer of energy between many waves. The triggering of this non-linear perturbation systematically coincides with a pedestal perturbation induced by the neutral beam injection beams and localized near the magnetic surface of safety factor q = 5. Among the non-linear interactions detected during the ELM by a bi-coherence analysis, the most active triad involves a slow frequency that is qualitatively consistent with a geodesic acoustic mode located at the same location, i.e., near the q = 5 surface.