Observation of parametric instabilities in the lower-hybrid range of frequencies in the Alcator C tokamak

Journal Article · Fri Mar 01 04:00:00 EST 1985 · Phys. Fluids; (United States)

OSTI ID:5941291

Takase, Y; Porkolab, M; Schuss, J J; Watterson, R L; Fiore, C L; Slusher, R E; Surko, C M

Parametric decay processes have been studied using rf probes and CO/sub 2/ laser scattering during the lower-hybrid wave heating and current drive experiments in the Alcator C tokamak. The most important process is believed to be the nonresonant decay into ion-cyclotron quasimodes and/or that into electron-Landau quasimodes. At lower densities ..omega../sub 0//..omega../sub lh/(0)>2 (where ..omega../sub 0/ is the frequency of the injected pump wave and ..omega../sub lh/(0) is the lower-hybrid frequency evaluated at the plasma center), where efficient current drive and electron heating are obtained, parametric decay is absent or very weak. At higher densities (..omega../sub 0//..omega../sub lh/(0) < or approx. =2) strong parametric decay is observed which correlates well with ion tail formation near the plasma edge. Above these densities the electron tail is no longer formed and no significant heating or current drive have been obtained. Parametric decay may be responsible, at least partially, for loss of wave power near the plasma periphery.

• Research Organization: Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
• DOE Contract Number: AC02-78ET51013
• OSTI ID: 5941291
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 28:3; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102 -- Fusion Energy-- Plasma Research-- Diagnostics
700107* -- Fusion Energy-- Plasma Research-- Instabilities
ALCATOR DEVICE
CLOSED PLASMA DEVICES
CURRENT-DRIVE HEATING
DECAY
DEUTERIUM
DISPERSION RELATIONS
ELECTRIC HEATING
ELECTROMAGNETIC RADIATION
ENERGY
HEATING
HIGH-FREQUENCY HEATING
HYDROGEN ISOTOPES
INSTABILITY
INSTABILITY GROWTH RATES
ISOTOPES
JOULE HEATING
LASER RADIATION
LIGHT NUCLEI
LIGHT SCATTERING
LOWER HYBRID HEATING
NUCLEI
ODD-ODD NUCLEI
PARAMETRIC INSTABILITIES
PLASMA
PLASMA DIAGNOSTICS
PLASMA HEATING
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PROBES
RADIATIONS
RADIOWAVE RADIATION
RESISTANCE HEATING
SCATTERING
STABLE ISOTOPES
THERMONUCLEAR DEVICES
THRESHOLD ENERGY
TOKAMAK DEVICES