Observation of ponderomotive and other non-linear effects produced by electrostatic waves in a magnetized low density plasma

Riccardi, C.; Fontanesi, M.; Penso, A; Sindoni, E.

doi:10.1016/0375-9601(95)00742-l

Cited by 6 publications

(3 citation statements)

References 14 publications

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“…A similar modification of the density profile was observed at different toroidal locations without remarkable differences. A comparison of profiles obtained for different frequencies of the RF signal [15] confirms that the ponderomotive effect is associated with the LHW as it mostly occurs before the conversion layer; this lies where the measured plasma density reaches the n lh value, which in the case of figure 3 is localized at r = 2 cm. In the presence of RF the electron temperature (figure 3(b)) increases up to three times.…”

Section: Plasma Profile Modifications Via Lhwmentioning

confidence: 53%

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RF-induced electric field and transport: experiments in non-fusion plasmas

Riccardi

Bevilacqua

Mozzi

et al. 1999

Plasma Phys. Control. Fusion

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The generation of radial electric fields through radiofrequency has been investigated in a toroidal magnetized plasma without rotational transform. By launching different kinds of electrostatic waves the plasma profiles were modified and sheared electric fields were generated. Direct observation of sheared E × B flows driven by fluctuations via Reynolds stress at the resonance layer of ion Bernstein is reported. These experiments provide a new bridge between experimental measurements and theoretical models in understanding the underlying physics of improved confinement regimes using RF in magnetically confined plasmas.

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Section: Plasma Profile Modifications Via Lhwmentioning

confidence: 53%

“…In the past, different experiments on e.s. wave propagation were performed in Thorello in linear and nonlinear conditions [14,15]. The excitation of IBW and LHW was successfully carried out and also used to diagnose plasma parameters.…”

Section: Introductionmentioning

confidence: 99%

RF-induced electric field and transport: experiments in non-fusion plasmas

Riccardi

Bevilacqua

Mozzi

et al. 1999

Plasma Phys. Control. Fusion

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“…[16][17][18] The PMF is largest in the immediate vicinity of the antenna and can deplete the density there significantly, creating a local cavity and steepening the density profile farther away from the antenna. These effects are well known in the context of lower-hybrid heating, [19][20][21] have been demonstrated experimentally in the ion cyclotron frequency range in a recent experiment, 22 and have been measured using microwave reflectometry on PBX-M 23 ͑Poloidal Beta Experiment-Modified͒ and Tokamak Fusion Test Reactor ͑TFTR͒. 24 The steepening of the density profile is expected to enhance the reflections of the EPW and lower the efficiency of the mode conversion to the IBW.…”

Section: Introductionmentioning

confidence: 95%

Role of ponderomotive density expulsion in ion Bernstein wave coupling to the core plasma

1998

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When the density at the ion Bernstein wave ͑IBW͒ antenna is relatively low, mode transformation of the electron plasma wave to the IBW is sensitive to the density gradient scale length, and hence to ponderomotive effects. A second-order nonlinear ordinary differential equation that describes mode transformation at the lower-hybrid layer, including self-consistent ponderomotive density profile modification, is solved for the rf electrostatic potential in front of the IBW antenna, for the particular case of heating just below the second harmonic of the deuterium cyclotron frequency. The complex antenna impedance and a local reflectivity are calculated, assuming vacuum within the antenna box. These calculations reveal diminished antenna coupling to the IBW with increasing ponderomotive density expulsion, as compared to the linear prediction. The ponderomotive force increases the density gradient in the edge plasma, thus enhancing reflection and lowering the loading resistance. The model also describes the direct launch of IBWs in high edge density regimes, lacking a lower-hybrid layer, where the impedance is found to be much smaller than in the low density regime.

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