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Frequency spectral broadening of lower hybrid waves in tokamak plasmas - causes and effects

Abstract

The frequency spectral broadening of lower hybrid (LH) waves injected into tokamak plasmas is extensively analyzed with reference mostly to experimental data from the ASDEX tokamak. The link between the magnitude of the pump spectral width and the degradation of the LH current drive efficiency (up to a factor of 2), pointed out in previous works, is explained. The experimental behaviour of LH power absorption is also well reproduced, even in situations when the access of the launched LH waves to the core plasma should be largely forbidden. Experiments are described that are aimed at determined whether parametric decay instabilities (PDIs) or scattering of LH waves by density fluctuations in the plasma edge are causes of the broadening of the LH pump frequency spectrum. Fluctuations emerge as the largely dominant process, while no signature of PDI processes is observed. Careful measurements of the density fluctuations in the ASDEX scrape-off layer plasma allow the analytical description given by Andrews and Perkins to be assumed as the appropriate model of LH scattering. Indeed, it supplies the correct magnitude for the frequency spectral width of the LH pump, and explains quantitatively, together with a ray tracing code, why the CD efficiency decreases with  More>>
Authors:
Pericoli Ridolfini, V; Giannone, L.; Bartiromo, R [1] 
  1. Associazione Euratom-ENEA sulla Fusione, Rome (Italy). Centro Ricerche Energia Frascati
Publication Date:
Apr 01, 1994
Product Type:
Journal Article
Reference Number:
AIX-25-054053; EDB-94-120818
Resource Relation:
Journal Name: Nuclear Fusion; (IAEA); Journal Volume: 34:4
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ASDEX TOKAMAK; LOWER HYBRID CURRENT DRIVE; EFFICIENCY; ENERGY SPECTRA; EXPERIMENTAL DATA; FLUCTUATIONS; LINE BROADENING; PLASMA DENSITY; PLASMA RADIAL PROFILES; PLASMA SCRAPE-OFF LAYER; SCATTERING; BOUNDARY LAYERS; CLOSED PLASMA DEVICES; DATA; INFORMATION; LAYERS; NON-INDUCTIVE CURRENT DRIVE; NUMERICAL DATA; SPECTRA; THERMONUCLEAR DEVICES; TOKAMAK DEVICES; VARIATIONS; 700350* - Plasma Production, Heating, Current Drive, & Interactions- (1992-)
OSTI ID:
7014119
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 0029-5515; CODEN: NUFUAU
Submitting Site:
INIS
Size:
Pages: 469-481
Announcement Date:
Sep 01, 1994

Citation Formats

Pericoli Ridolfini, V, Giannone, L., and Bartiromo, R. Frequency spectral broadening of lower hybrid waves in tokamak plasmas - causes and effects. IAEA: N. p., 1994. Web. doi:10.1088/0029-5515/34/4/I01.
Pericoli Ridolfini, V, Giannone, L., & Bartiromo, R. Frequency spectral broadening of lower hybrid waves in tokamak plasmas - causes and effects. IAEA. doi:10.1088/0029-5515/34/4/I01.
Pericoli Ridolfini, V, Giannone, L., and Bartiromo, R. 1994. "Frequency spectral broadening of lower hybrid waves in tokamak plasmas - causes and effects." IAEA. doi:10.1088/0029-5515/34/4/I01. https://www.osti.gov/servlets/purl/10.1088/0029-5515/34/4/I01.
@misc{etde_7014119,
title = {Frequency spectral broadening of lower hybrid waves in tokamak plasmas - causes and effects}
author = {Pericoli Ridolfini, V, Giannone, L., and Bartiromo, R}
abstractNote = {The frequency spectral broadening of lower hybrid (LH) waves injected into tokamak plasmas is extensively analyzed with reference mostly to experimental data from the ASDEX tokamak. The link between the magnitude of the pump spectral width and the degradation of the LH current drive efficiency (up to a factor of 2), pointed out in previous works, is explained. The experimental behaviour of LH power absorption is also well reproduced, even in situations when the access of the launched LH waves to the core plasma should be largely forbidden. Experiments are described that are aimed at determined whether parametric decay instabilities (PDIs) or scattering of LH waves by density fluctuations in the plasma edge are causes of the broadening of the LH pump frequency spectrum. Fluctuations emerge as the largely dominant process, while no signature of PDI processes is observed. Careful measurements of the density fluctuations in the ASDEX scrape-off layer plasma allow the analytical description given by Andrews and Perkins to be assumed as the appropriate model of LH scattering. Indeed, it supplies the correct magnitude for the frequency spectral width of the LH pump, and explains quantitatively, together with a ray tracing code, why the CD efficiency decreases with the broadening of the pump spectrum. It can also account for the observed LH power absorption coefficient. (author). 48 refs, 13 figs, 2 tabs.}
doi = {10.1088/0029-5515/34/4/I01}
journal = {Nuclear Fusion; (IAEA)}
volume = {34:4}
journal type = {AC}
place = {IAEA}
year = {1994}
month = {Apr}
}