Parametric excitation of ion-sound quasimodes during lower-hybrid heating experiments in tokamaks

Journal Article · Sat Oct 01 04:00:00 EDT 1983 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.864022· OSTI ID:5592001

Takase, Y; Porkolab, M

Parametric decay of a lower-hybrid pump wave into another lower-hybrid wave and a low-frequency ion-sound quasimode (..omega../sub R/roughly-equalk/sub parallel/v/sub t/i) is studied. Such an instability may be excited during high-power lower-hybrid heating experiments in tokamak plasmas and may lead to strong modification of the incident n/sub parallel/ spectrum near the plasma periphery. Such an instability could explain the broadened and downshifted frequency spectrum and phase-independent heating observed in the Alcator A tokamak experiments. Although the growth rate for this decay increases like ..gamma..+GAMMA/sub 2/proportionalE/sup 2//sub 0/ for powers slightly above threshold (GAMMA/sub 2/ is the linear damping rate at the lower sideband and E/sub 0/ is the pump electric field), for powers well above threshold (such that ..gamma..> or approx. =..omega../sub R/)..gamma..proportionalE/sup 2/3//sub 0/, and the convective thresholds are rather high. However, for inaccessible n/sub 0parallel/, the pump wave power is expected to accumulate on the outer surface of the plasma column where the growth rate is large and the convective thresholds are significantly reduced. In such a case the threshold pump power can become quite low and may be exceeded in experiments such as Alcator A.

• Research Organization: Department of Physics and Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
• DOE Contract Number: AC02-78ET51013
• OSTI ID: 5592001
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 26:10; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101 -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
700107* -- Fusion Energy-- Plasma Research-- Instabilities
CLOSED PLASMA DEVICES
DATA
HEATING
HIGH-FREQUENCY HEATING
INFORMATION
INSTABILITY
INSTABILITY GROWTH RATES
ION ACOUSTIC WAVES
ION WAVES
LOWER HYBRID HEATING
NUMERICAL DATA
PARAMETRIC INSTABILITIES
PLASMA
PLASMA HEATING
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA WAVES
POWER
THERMONUCLEAR DEVICES
TOKAMAK DEVICES