Resonant parametric excitations driven by lower‐hybrid fields

Villalón, E.

doi:doi:10.1063/1.862926

Volume/Page
Keyword
DOI
Citation
Advanced

Volume: Page/Article:

Search Content Type

article doi:

Citation:

Heating of a toroidal plasma by a nonuniform radio frequency field

Nonuniform electric fields created by an oscillating (1.8 MHz) dipole magnetic field are applied to a preformed, argon plasma in a torus with major radius R=19 cm, minor radius a=2.5 cm, and a toroidal magnetic field Ba=0.3 T. The induced rf plasma current flows in opposite toroidal directions in the outer (larger major radius) and inner regions of the plasma. Spatially and temporally resolved measurements are made of the electron density and temperature as well as the induced electric field and...

Thermal and radiation losses in a linear device

An analysis is presented of the electron temperature in a linear device which includes the effect of thermal conduction, heat flux limit, radiation, and end plugs. It is found that the thermal conduction and the heat flux limit are dominant in the initial phase of cooling, while the later phase is almost completely controlled by radiation that spatially homogenizes the temperature distribution. In the case of bremsstrahlung, within the frame of the present model, the temperature decays to zero i...

Three‐wave parametric excitation in inhomogeneous plasmas is examined in a two‐dimensional geometry relevant to supplementary rf heating of tokamaks. The stabilization of resonant parametric excitation due to a linear mismatch in wavenumbers and to the Landau‐damping rates of the decay waves is analyzed, assuming that the magnitude of the pump field is constant in time and in the spatial region where the resonant interaction takes place. Both types of temporally growing modes and spatially amplified instabilities are studied, using a WKB analysis. It is shown that either by increasing the strength of the mismatch K′ or the width of the pump L, the growth rate of the fastest growing normal mode will decrease. When the excited waves are slightly damped, it is shown that there exists a finite value of the product K′L, such that, above it, no temporal normal modes are excited. The amount of spatial amplification is also reduced by the mismatch in wavenumbers and by the damping rates of the excited waves. Because of the finite spatial extent of the pump electric field, the amplification length is found to be smaller than or equal to L, depending on the strength of the mismatch and damping rates.

KEYWORDS and PACS

Keywords

PLASMA HEATING, INHOMOGENEOUS PLASMA, TOKAMAK DEVICES, PLASMA WAVES, NONLINEAR PROBLEMS, HIGH−FREQUNCY HEATING, PARAMETRIC INSTABILITIES, LANDAU DAMPING, WKB APPROXIMATION, NORMAL−MODE ANALYSIS, BOUNDARY CONDITIONS, TWO−DIMENSIONAL CALCULATIONS, DISPERSION RELATIONS

PACS

52.50.Gj

Plasma heating by particle beams
52.35.Mw

Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.55.Fa

Tokamaks, spherical tokamaks
52.55.Hc

Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices