Abstract Details
Abstracts
Author: Vinicius Duarte
Requested Type: Poster
Submitted: 2025-03-12 15:43:47
Co-authors: E. J. Hartigan-O'Connor, N. N. Gorelenkov, J. B. Lestz
Contact Info:
Princeton Plasma Physics Laboratory
100 Stellarator Rd
Princeton, NJ 08543
United States
Abstract Text:
Quasilinear simulations can be an effective reduced tool for predicting and interpreting fast ion transport in fusion devices. At the core of these transport models is the form of their diffusion coefficients (or resonance functions), which have a leading role in determining the resonant wave saturation levels. While conventional quasilinear theory requires a random phase approximation to be satisfied via resonance overlap, it has been shown that near-threshold instabilities are naturally in the quasilinear regime even in the absence of any overlap, provided that the effective scattering rate felt by resonance particles well exceeds the instability net growth rate. This further motivates the deployment of resonance broadened quasilinear models to predict the dynamics of discrete Alfvénic eigenmodes upon their interaction with energetic ions, as they may alternate between the isolated and overlapping regimes. This work describes how a generalization of the resonance function can be constructed to automatically enforce quasilinear simulations to replicate saturation levels obtained from nonlinear simulations across any level of marginality. The resonance function is intuitively proposed in a convolutional form in phase space, to encode the following properties: (i) its characteristic broadening is the sum of the broadenings of the two individual components due to the effective scattering and due to wave amplitude, (ii) the resonance function integrates to the unity, as physically expected for a broadened function replacing a delta function, and (iii) it exactly recovers either of its constituents in the limits of marginal or strongly driven instability. Stability boundaries between pulsating and quasi-steady amplitudes are investigated in quasilinear simulations and the results are compared with fully nonlinear kinetic simulations. It is found that the resonance broadening width is the key parameter that determines the mode evolution properties.
Characterization: 1.0
Comments:
If possible, please place my poster next to the ones by Emma Devin and Eamon Hartigan-O'Connor.