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Title: Nonlinear lower hybrid modeling in tokamak plasmas

We present here new results concerning the nonlinear mechanism underlying the observed spectral broadening produced by parametric instabilities occurring at the edge of tokamak plasmas in present day LHCD (lower hybrid current drive) experiments. Low frequency (LF) ion-sound evanescent modes (quasi-modes) are the main parametric decay channel which drives a nonlinear mode coupling of lower hybrid (LH) waves. The spectrum of the LF fluctuations is calculated here considering the beating of the launched LH wave at the radiofrequency (RF) operating line frequency (pump wave) with the noisy background of the RF power generator. This spectrum is calculated in the frame of the kinetic theory, following a perturbative approach. Numerical solutions of the nonlinear LH wave equation show the evolution of the nonlinear mode coupling in condition of a finite depletion of the pump power. The role of the presence of heavy ions in a Deuterium plasma in mitigating the nonlinear effects is analyzed.
Authors:
;  [1] ; ;  [2]
  1. Università Roma Tre, Dipartimento di Ingegneria, Roma (Italy)
  2. Associazione EURATOM/ENEA sulla Fusione, Centro Ricerche Frascati (Italy)
Publication Date:
OSTI Identifier:
22263888
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1580; Journal Issue: 1; Conference: 20. topical conference on radiofrequency power in plasmas, Sorrento (Italy), 25-28 Jun 2013; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COUPLING; DECAY; DEUTERIUM; HEAVY IONS; LINE BROADENING; LOWER HYBRID CURRENT DRIVE; LOWER HYBRID HEATING; PARAMETRIC INSTABILITIES; PLASMA; SIMULATION; SPECTRA; TOKAMAK DEVICES; WAVE EQUATIONS