The absorption of electron cyclotron waves in the vicinity of an extremum of the equilibrium magnetic field

Journal Article · Tue May 01 04:00:00 EDT 1990 · Physics of Fluids B; (USA)

DOI:https://doi.org/10.1063/1.859575· OSTI ID:7185132

Lashmore-Davies, C N; Dendy, R O; Hastie, R J ^[1]

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1. Culham Laboratory, Abingdon, Oxfordshire OX14 3DB, England (GB)

Local extrema in the equilibrium magnetic field strength can occur in tokamak plasmas when the plasma beta is increased. Furthermore, the magnetic field strength experienced by an electromagnetic wave propagating along a vertical chord in lower-beta tokamak plasmas may also pass through an extremum. For both these reasons, it is of interest to calculate the absorption of electron cyclotron waves in configurations where a harmonic of the cyclotron resonance lies near an extremum of the equilibrium magnetic field strength. It is shown that strong absorption can occur for both the O mode at second harmonic resonance and the X mode at third harmonic resonance, whereas absorption at these resonances is relatively weak when the gradient in magnetic field strength is linear. The optical depth in a magnetic field with parabolic scale length {ital L} is typically enhanced with respect to that in a field with linear scale length {ital R} by a factor {ital cL}/5{ital v}{sub {ital T}}{ital R}, where {ital v}{sub {ital T}} is the electron thermal velocity and {ital c} the velocity of light. Since electron cyclotron waves can reach these resonances in high-density plasma from launch positions on the low-field side of the tokamak, the number of effective and convenient electron cyclotron heating configurations is increased when the equilibrium magnetic field strength has local extrema.

• OSTI ID: 7185132
• Journal Information: Physics of Fluids B; (USA), Journal Name: Physics of Fluids B; (USA) Vol. 2:5; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101 -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
ABSORPTION
CLOSED PLASMA DEVICES
CYCLOTRON HARMONICS
CYCLOTRON RESONANCE
DISPERSION RELATIONS
ENERGY ABSORPTION
ENERGY RANGE
EQUILIBRIUM
HARMONICS
HEATING
HIGH-BETA PLASMA
HIGH-FREQUENCY HEATING
ICR HEATING
LOW-BETA PLASMA
MAGNETIC FIELDS
MASS
OSCILLATIONS
PLASMA
PLASMA HEATING
RELATIVISTIC RANGE
RESONANCE
THERMONUCLEAR DEVICES
TOKAMAK DEVICES