Experimental study of high power mm-waves scattering by plasma turbulence in TCV plasmas

O Chellaï,P Papagiannis,L Figini,I Furno,C Tsironis,D Ricci,A Koehn,L Hizanidis,S Alberti,T Goodman,J Hillairet

doi:10.1051/epjconf/201715703008

Abstract

Understanding the propagation of high power mm-wave in plasmas is of tremendous importance in the route to fusion considering their extensive use in magnetically confined fusion devices. Mm-beams, launched from the outside of the vessel must propagate through plasma edge-turbulence before reaching their target region. Until recently, the effect of edge-turbulence on the beam propagation was neglected, but it has been estimated for ITER that it could lead to significant differences in the time-averaged and instantaneous beam profiles, leading to a loss of efficiency in their use. In this paper, we present first direct experimental measurements of high power beam after propagation in simple magnetized toroidal plasmas in TCV.

Highlights

High power mm-waves are extensively used in tokamaks by locally driving plasma current to stabilize neoclassical tearing modes (NTMs) [1]
We present first direct poloidal measurements of high power (≈ 100kW) third electron cyclotron harmonic beam in the Tokamak à Configuration Variable (TCV) after propagation in a turbulent plasma in a simple magnetized torus (SMT) configuration
The effect of plasma edge turbulence on the propagation of a high-power mm-beam is investigated in TCV

Summary

Introduction

High power mm-waves are extensively used in tokamaks by locally driving plasma current to stabilize neoclassical tearing modes (NTMs) [1]. The SOL is localized at the edge of the tokamak plasma and is characterized by large electron density fluctuations (up to 100% of the background density) associated with field-aligned filaments, commonly referred to as blobs [2]. In future large tokamaks, such as ITER, the path length of the beam will be long enough to enable small perturbations in the SOL to cause significant changes in both the time averaged and instantaneous beam profiles. This may lead to its broadening on average [3] and to a loss of efficiency in NTM stabilization [4]. There is still a need for experimental data to validate the simulation tools and reach predictive capabilities for ITER and beyond

Methods

Results

Conclusion