Perpendicular momentum injection by lower hybrid wave in a tokamak

TL;DR

This paper investigates how lower hybrid waves inject perpendicular momentum into a tokamak, affecting plasma rotation and momentum transfer mechanisms, with a detailed quasilinear analysis of electron and ion interactions.

Contribution

It provides a novel quasilinear framework showing both perpendicular and parallel momentum transfer from lower hybrid waves to plasma electrons and ions.

Findings

Perpendicular momentum transfer causes outward electron pinch.

Parallel momentum is transferred via collisions.

The wave's poloidal momentum increases during propagation.

Abstract

The injection of lower hybrid waves for current drive into a tokamak affects the profile of intrinsic rotation. In this article, the momentum deposition by the lower hybrid wave on the electrons is studied. Due to the increase in the poloidal momentum of the wave as it propagates into the tokamak, the parallel momentum of the wave increases considerably. The change of the perpendicular momentum of the wave is such that the toroidal angular momentum of the wave is conserved. If the perpendicular momentum transfer via electron Landau damping is ignored, the transfer of the toroidal angular momentum to the plasma will be larger than the injected toroidal angular momentum. A proper quasilinear treatment proves that both perpendicular and parallel momentum are transferred to the electrons. The toroidal angular momentum of the electrons is then transferred to the ions via different mechanisms for the parallel and perpendicular momentum. The perpendicular momentum is transferred to ions through an outward radial electron pinch, while the parallel momentum is transferred through collisions.