title: Resilience of quasi-isodynamic stellarators against trapped-particle instabilities.
abstract: It is shown that in perfectly quasi-isodynamic stellarators, trapped particles with a bounce frequency much higher than the frequency of the instability are stabilizing in the electrostatic and collisionless limit. The collisionless trapped-particle instability is therefore stable as well as the ordinary electron-density-gradient-driven trapped-electron mode. This result follows from the energy balance of electrostatic instabilities and is thus independent of all other details of the magnetic geometry.
authors.affiliation: Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstraße 1, 17491 Greifswald, Germany.
authors.forename: J H E
authors.initials: JH
authors.lastname: Proll
authors.forename: P
authors.initials: P
authors.lastname: Helander
authors.forename: J W
authors.initials: JW
authors.lastname: Connor
authors.forename: G G
authors.initials: GG
authors.lastname: Plunk