Scanning edge plasma pedestal parameters for plasma stability studies

• Grant number: 25/04335-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2025
• End date: December 31, 2025
• Field of knowledge: Physical Sciences and Mathematics - Physics - Physics of Fluids, Plasma Physics and Electrical Discharge
• Principal Investigator: Gustavo Paganini Canal
• Grantee: João Vitor Araya Kobayashi de Sousa
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 22/04857-2 - Development of an innovative set of ELM control coils for the TCABR tokamak, AP.JP

Abstract

Most of the initial studies on edge localized modes (ELMs) in tokamaks have focused on magnetohydrodynamic (MHD) stability calculations. These early works focused on infinite toroidal mode number (n) ballooning modes and low-n kink modes. Subsequent works emphasized the role of intermediate-n (3 < n < 40), coupled peeling-ballooning (P-B) modes as the limiting plasma instability in the pedestal region. These studies led to what is nowadays referred to as the P-B model of ELM triggering. A key element of this model is that P-B modes provide an effective limit on the pedestal height (at a given pedestal width) above which ELMs are driven. In the P-B picture, the sharp edge pressure gradients, and the consequent large parallel bootstrap current, in the pedestal region provide the free energy that can destabilize peeling and ballooning modes over a wide range of toroidal mode numbers. These intermediate-n P-B modes impose constraints on the pedestal height, which depend of the pedestal width, plasma shape, collisionality, safety factor, and other equilibrium parameters. In this work, a set of synthetic MHD equilibria will be generated, with various edge parameters being scanned, such as pedestal pressure gradient, pedestal width, collisionality, plasma beta, edge parallel current density, among others. These equilibria will then be used to identify the P-B marginal stability boundary in future TCABR ohmic H-mode plasmas. (AU)