Speaker
Description
Max-Planck-Institut für Plasmaphysik
Within the gyrokinetic formalism [1-2], we present the equations for an explicit treatment of the electromagnetic version of the collisionless Universal/Trapped-Electron, and Microtearing modes, in general geometry. The gradient of the plasma , the ratio of kinetic to magnetic pressure, is taken to be small enough to avoid perturbations of the magnetic field strength [3]. We highlight the role of trapped electrons in the resonant destabilization, or damping, via electromagnetic corrections to ideal Ohms's law, for electron-temperature-gradient driven modes whose frequency relates to the bounce-averaged electron curvature drift. We then investigate the stability properties of maximum-J devices [4] (where J is the second adiabatic invariant) at finite , that is, in the regime in which the maximum-J condition is more likely to be satisfied. Nonlinear energetic arguments will also be given.
References:
[1] W. M. Tang, J. W. Connor, and R. J. Hastie, Nucl. Fusion 20, 1493 (1980)
[2] E. A. Frieman , and L. Chen, Phys. Fluids 25, 502 (1982)
[3] A. Zocco, P. Helander, and J. W. Connor Plasma Phys. Control. Fusion 57 085003 (2015)
[4] P. Helander, Reports on Progress in Physics, 77, 08701 (2014)
