Speaker
Description
This contribution explores the detailed drive of Alfvén eigenmode activity in dedicated KSTAR energetic particle experiments. The broad purpose of these experiments has been to develop scenarios to study energetic particle driven modes, as well as enable experimental studies of wave-particle-plasma interaction and particle loss at higher beam power. To date, the authors have reported the drive of beta-induced Alfvén eigenmodes [1], and bursty chirping modes observed during early NBI heating [2]. This contribution focuses on discharge campaigns in 2020 and 2021 which involve scans over NBI power, pulse width modulation, and perveance to excite and select the Alfvénic mode of interest, followed by application of 3D Resonant Magnetic Perturbation coils with different phasing and current waveforms. Of particular interest is a series of discharges in which an increasing amplitude of n = 1 resonant magnetic perturbation (RMP) was applied to a reference scenario with n = 2 and n = 3 toroidal Alfvén eigenmodes (TAE’s) modulated by a tearing mode with n = 1, 2 and 3 harmonics. As the n = 1 RMP amplitude increases, density pump-out occurs and TAEs are suppressed. At sufficiently high RMP amplitude the plasma disrupts. To understand the underlying RMP interaction with TAEs physics, in the last 6 months we have carried out detailed TRANSP analysis and the Alfvénic stability simulations using the gyro-fluid code FAR3D [3]. These will be reported in this work.
[1] M J Hole et al 2013 Plasma Phys. Control. Fusion 55 045004
[2] M J Hole et al 2019 Plasma Phys. Control. Fusion 61 025016
[3] Varela J, et al 2024, Front. Phys. 12:1422411.
