TY - JOUR

T1 - Electron cyclotron current drive simulations for finite collisionality plasmas in Wendelstein 7-X using the full linearized collision model

AU - Kapper, Gernot

AU - Kasilov, Sergei V.

AU - Kernbichler, Winfried

AU - Martitsch, Andreas Frank

AU - Heyn, Martin F.

AU - Marushchenko, Nikolai B.

AU - Turkin, Yuriy

PY - 2016/11/30

Y1 - 2016/11/30

N2 - The Electron Cyclotron Current Drive (ECCD) efficiency is usually modeled in the collisionless limit. While such models are sufficient for plasmas with rather low collisionality, they might underestimate the current drive in plasmas at low temperatures likely to occur at the initial phase of high density device operation. In this paper, the impact of finite collisionality effects on the wave-induced current drive is studied for a high-mirror configuration of Wendelstein 7-X using a combination of the drift kinetic equation solver NEO-2 and the ray-tracing code TRAVIS for a realistic set of plasma parameter profiles. The generalized Spitzer function, which describes the ECCD efficiency in phase space, is modeled with help of NEO-2, which uses the full linearized Coulomb collision operator, including energy and momentum conservation. Within this approach, the linearized drift kinetic equation is solved by means of the field line integration technique without any simplifications on device geometry. The results of the ray-tracing code TRAVIS using the ECCD efficiency from NEO-2 within the adjoint approach show a significant difference for the driven current when compared to commonly used collisionless models for the ordinary as well as the extraordinary second harmonic mode.

AB - The Electron Cyclotron Current Drive (ECCD) efficiency is usually modeled in the collisionless limit. While such models are sufficient for plasmas with rather low collisionality, they might underestimate the current drive in plasmas at low temperatures likely to occur at the initial phase of high density device operation. In this paper, the impact of finite collisionality effects on the wave-induced current drive is studied for a high-mirror configuration of Wendelstein 7-X using a combination of the drift kinetic equation solver NEO-2 and the ray-tracing code TRAVIS for a realistic set of plasma parameter profiles. The generalized Spitzer function, which describes the ECCD efficiency in phase space, is modeled with help of NEO-2, which uses the full linearized Coulomb collision operator, including energy and momentum conservation. Within this approach, the linearized drift kinetic equation is solved by means of the field line integration technique without any simplifications on device geometry. The results of the ray-tracing code TRAVIS using the ECCD efficiency from NEO-2 within the adjoint approach show a significant difference for the driven current when compared to commonly used collisionless models for the ordinary as well as the extraordinary second harmonic mode.

U2 - http://dx.doi.org/10.1063/1.4968234

DO - http://dx.doi.org/10.1063/1.4968234

M3 - Article

SN - 1089-7674

VL - 23

SP - 112511

JO - Physics of Plasmas

JF - Physics of Plasmas

IS - 11

ER -