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  4. Impact of microwave beam scattering by density fluctuations on the electron-cyclotron power deposition profile in tokamaks
 
research article

Impact of microwave beam scattering by density fluctuations on the electron-cyclotron power deposition profile in tokamaks

Cazabonne, Jean Arthur  
•
Coda, S  
•
Decker, J.
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February 1, 2024
Nuclear Fusion

Electron-cyclotron waves are a tool commonly used in tokamaks, in particular to drive current. Their ability to drive current in a very localized manner renders them an optimal tool for MHD mode mitigation. However, such applications require high accuracy and good control of the power deposition location to efficiently target the magnetic islands. It has been indirectly observed that the suprathermal electron distribution, resulting from the wave absorption, is broader than what is expected from experimentally-constrained forward drift-kinetic modeling. The present paper explores the possibility that beam scattering through the turbulent edge of the plasma may explain this observed discrepancy. In particular, full-wave studies exhibit three beam broadening regimes, from superdiffusive to diffusive, with an intermediate regime characterized by a Lorentzian beam profile with a slightly increased full-width at half maximum with respect to the quiet plasma case. In the tokamak a configuration variable, dedicated plasma scenarios have been developed to test this hypothesis. A realistic worst-case fluctuation scenario falls into this intermediate beam broadening regime. By comparing the experimental hard x-ray emission from suprathermal electron Bremmstrahlung with the emission calculated by coupling a full-wave model to a Fokker-Planck solver, it is shown that, in the tested cases, the beam broadening is not sufficient to explain the aforementioned discrepancy between simulation and experiment and that another mechanism must play the main role in broadening the suprathermal electron distribution.

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Type
research article
DOI
10.1088/1741-4326/ad1af6
Web of Science ID

WOS:001142819300001

Author(s)
Cazabonne, Jean Arthur  
Coda, S  
Decker, J.
Krutkin, Oleg  
Kumar, Umesh  
Peysson, Y.
Corporate authors
TCV Team
Date Issued

2024-02-01

Publisher

IOP Publishing Ltd

Published in
Nuclear Fusion
Volume

64

Issue

2

Article Number

026019

Subjects

Physical Sciences

•

Tokamak

•

Electron-Cyclotron

•

Hard X-Ray Spectrometry

•

Density Fluctuations

•

Beam Scattering

•

Fokker-Planck Simulations

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SPC  
FunderGrant Number

Schweizerischer Nationalfonds zur Frderung der Wissenschaftlichen Forschunghttp://dx.doi.org/10.13039/501100001711

101052200

Swiss National Science Foundation - European Union via the Euratom Research and Training Programme

Swiss State Secretariat for Education, Research and Innovation (SERI)

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Available on Infoscience
February 21, 2024
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/205058
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