NONLINEAR EFFECTS IN RF PLASMAS
In spite of a strong reference for the linear character of wave propagation in RF heating and current drive experiments in tokamaks, in the case of the spectral gap problem in LH wave heating and current drive it is hard to deny that the wave - plasma interaction is dominated by some nonlinear effect. In order to explain this phenomenon, we show that the original k-spectrum of a LH pump decays substantially as a result of a secular (in space) effect due to the ponderomotive density change. We stress that even a wave with arbitrarily small amplitude is non-linearly distorted and breaks if it penetrates deeply enough into the plasma. In these last properties such a nonlinear effect is reminiscent of an otherwise entirely different situation: the relativistic motion of a charged particle in a constant magnetic field and a circularly polarized electromagnetic wave propagating along the field. Even if the amplitude is so small that the particle speed constantly remains arbitrarily low, the motion becomes completely relativistic after a sufficiently long interaction time.
Bibliographic Reference: COURSE AND WORKSHOP ON APPLICATIONS OF RF WAVES TO TOKAMAK PLASMAS, VILLA MONASTERO, VARENNA (ITALY), SEPT. 5-14, 1985 PP. 583-619, VOL. II 908 P., 1985, VOL. I AND VOL. II WRITE TO MONOTYPIA FRANCHI, VIALE UMBRIA 28/C, 06012 CITTA DI CASTELLO, PERUGIA (I
Record Number: 1989124101000 / Last updated on: 1987-01-01
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