Propagation and damping of lower hybrid fast waves in a tokamak plasma
Thesis/Dissertation
·
OSTI ID:5126013
The propagation and damping of the Lower Hybrid Fast Waves (LHFW) have been studied in detail in the UCLA Continuous Current Tokamak (CCT) in both test wave and high power current drive experiments. Anomalous damping of LHFW launched by conventional antennas has been observed in CCT over a wide range of frequencies and magnetic fields during high power Fast Wave Current Drive (FWCD) experiments. The fast wave damping is 10-100 times larger than expected from either Landau or collisional damping. In order to identify the wave damping mechanisms, insertible magnetic dipole antennas have been used to launch test waves locally. The damping length of the LHFW was determined to be {approximately}30cm in CCT using detailed poloidal field maps at various distances from the antennas. Lorentzian shaped sidebands, observed to be excited strongly near the fundamental and harmonics of the driver frequencies are very well correlated with the local density fluctuation spectra. At low power levels, the sideband spectra are independent of power and carrier frequencies suggesting that scattering rather than parametric processes are responsible for its generation. The author has chosen the wave scattering theory developed by S. N. Antani and D. J. Kaup to compare with the experiments mainly because of its simplicity. There are however, several problems in their paper: (1) An incorrect approximation using the expression Im(n {perpendicular}) {approx} (Im(n {perpendicular}{sup 2})){sup 1/2} has resulted in the overestimation of the wave damping by a factor of 10{sup 3}-10{sup 5} in the final solution. Upon correction he is able to get good agreement between the theory and the experiment. (2) At small n{sub {parallel}}, their fast wave approximation is no longer valid. The original theory has been examined in detail and he has generalized it to a full-wave formalism.
- Research Organization:
- California Univ., Los Angeles, CA (United States)
- OSTI ID:
- 5126013
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
700108 -- Fusion Energy-- Plasma Research-- Wave Phenomena
ANTENNAS
CLOSED PLASMA DEVICES
DAMPING
ELECTRICAL EQUIPMENT
EQUIPMENT
HARMONICS
HEATING
HIGH-FREQUENCY HEATING
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
NON-INDUCTIVE CURRENT DRIVE
OSCILLATIONS
PLASMA HEATING
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
WAVE PROPAGATION
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
700108 -- Fusion Energy-- Plasma Research-- Wave Phenomena
ANTENNAS
CLOSED PLASMA DEVICES
DAMPING
ELECTRICAL EQUIPMENT
EQUIPMENT
HARMONICS
HEATING
HIGH-FREQUENCY HEATING
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
NON-INDUCTIVE CURRENT DRIVE
OSCILLATIONS
PLASMA HEATING
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
WAVE PROPAGATION