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Title: Theory of anomalous backscattering in second harmonic X-mode ECRH experiments

Abstract

A quantitative model explaining generation of the anomalous backscattering signal in the second harmonic X-mode electron cyclotron resonance heating (ECRH) experiments at TEXTOR tokamak as a secondary nonlinear process which accompanies a primary low-threshold parametric decay instability (PDI) leading to excitation of two—upper hybrid (UH)—plasmons trapped in plasma is developed. The primary absolute PDI enhancing the UH wave fluctuations from the thermal noise level is supposed to be saturated due to a cascade of secondary low-threshold decays of the daughter UH wave leading to excitation of the secondary UH waves down-shifted in frequency and the ion Bernstein wave. A set of equations describing the cascade is derived and solved numerically. The results of numerical modelling are shown to be in agreement with the analytical estimations of the growth rate of the initial and secondary parametric decays and the saturation level. The generation of backscattering signal is explained by coupling of the daughter UH waves. The fine details of the frequency spectrum of the anomalously reflected extraordinary wave and the absolute value of the observed backscattering signal in the second harmonic X-mode ECRH experiments at TEXTOR are reproduced.

Authors:
;  [1]
  1. Ioffe Institute, 26 Polytekhnicheskaya st., St. Petersburg 194021 (Russian Federation)
Publication Date:
OSTI Identifier:
22599978
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BACKSCATTERING; BERNSTEIN MODE; COMPUTERIZED SIMULATION; CYCLOTRONS; DECAY; DECAY INSTABILITY; ECR HEATING; ELECTRON CYCLOTRON-RESONANCE; ELECTRONS; EQUATIONS; EXCITATION; FLUCTUATIONS; NONLINEAR PROBLEMS; PLASMA WAVES; PLASMONS; SATURATION; SIGNALS; TEXTOR TOKAMAK

Citation Formats

Gusakov, E. Z., and Popov, A. Yu.. Theory of anomalous backscattering in second harmonic X-mode ECRH experiments. United States: N. p., 2016. Web. doi:10.1063/1.4959849.
Gusakov, E. Z., & Popov, A. Yu.. Theory of anomalous backscattering in second harmonic X-mode ECRH experiments. United States. doi:10.1063/1.4959849.
Gusakov, E. Z., and Popov, A. Yu.. Mon . "Theory of anomalous backscattering in second harmonic X-mode ECRH experiments". United States. doi:10.1063/1.4959849.
@article{osti_22599978,
title = {Theory of anomalous backscattering in second harmonic X-mode ECRH experiments},
author = {Gusakov, E. Z. and Popov, A. Yu.},
abstractNote = {A quantitative model explaining generation of the anomalous backscattering signal in the second harmonic X-mode electron cyclotron resonance heating (ECRH) experiments at TEXTOR tokamak as a secondary nonlinear process which accompanies a primary low-threshold parametric decay instability (PDI) leading to excitation of two—upper hybrid (UH)—plasmons trapped in plasma is developed. The primary absolute PDI enhancing the UH wave fluctuations from the thermal noise level is supposed to be saturated due to a cascade of secondary low-threshold decays of the daughter UH wave leading to excitation of the secondary UH waves down-shifted in frequency and the ion Bernstein wave. A set of equations describing the cascade is derived and solved numerically. The results of numerical modelling are shown to be in agreement with the analytical estimations of the growth rate of the initial and secondary parametric decays and the saturation level. The generation of backscattering signal is explained by coupling of the daughter UH waves. The fine details of the frequency spectrum of the anomalously reflected extraordinary wave and the absolute value of the observed backscattering signal in the second harmonic X-mode ECRH experiments at TEXTOR are reproduced.},
doi = {10.1063/1.4959849},
journal = {Physics of Plasmas},
number = 8,
volume = 23,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2016},
month = {Mon Aug 15 00:00:00 EDT 2016}
}