Physics of drift Alfven instabilities and energetic particles in fusion plasmas

Shear Alfven wave (SAW)/drift Alfven wave (DAW) fluctuations can be destabilized by energetic particles (EPs) as well as thermal plasma components, which play a key role in the EP energy and momentum transport processes in burning fusion plasmas. The drift Alfven energetic particle stability (DAEPS) code, which is an eigenvalue code using the finite element method, was developed to analyze Alfven instabilities excited by EPs. The model equations, consisting of the quasineutrality condition and the Schrodinger-like form of the vorticity equation, are derived within the general fishbone-like dispersion relation theoretical framework, which is widely used to analyze SAW/DAW physics. The mode structure decomposition approach and asymptotic matching between the inertial/singular layer and ideal regions are adopted. Therefore, the DAEPS code can provide not only frequency and growth/damping rate but also the parallel mode structure as well as the asymptotic behavior corresponding to the singular-layer contribution. Thus, it fully describes fluid and kinetic continuous spectra as well as unstable and damped modes. The model equations have been extended to include general axisymmetric geometry and to solve for the response of circulating and trapped particles by means of the action-angle approach. In this work, we discuss linear dispersion relation and parallel mode structure of drift Alfven instabilities excited by EPs, computed with the DAEPS code with realistic experimental plasma profile and magnetic configuration. We compare DAEPS results with FALCON/LIGKA to provide a verification of the code. We then adopt the Dyson-Schrodinger model (DSM) to further analyze the EP energy and momentum flux. We will briefly discuss how the parallel mode structure of the drift Alfven instabilities can be used in the DSM to calculate the nonlinear radial envelope evolution and the EP transport.

Automated summary

Shear Alfven wave (SAW)/drift Alfven wave (DAW) fluctuations can be destabilized by energetic particles (EPs) and thermal plasma components, influencing energy and momentum transport in fusion plasmas. The drift Alfven energetic particle stability (DAEPS) code is a finite element eigenvalue code used to analyze EP-excited Alfven instabilities. The code provides frequency, growth/damping rate, parallel mode structure, and asymptotic behavior, describing fluid and kinetic spectra as well as stable and unstable modes. The model equations have been extended to include general axisymmetric geometry and the response of circulating and trapped particles. This work discusses the linear dispersion relation and parallel mode structure of DAEPS-computed drift Alfven instabilities, and uses the Dyson-Schrodinger model to analyze EP energy and momentum flux.