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The conventional ordinary O-mode and the extraordinary X-mode in the electron cyclotron range of frequencies are not suitable for core heating in high-β spherical tokamak plasmas, like the National as they are weakly damped at high harmonics of the electron cyclotron frequency. However, electron Bernstein waves (EBW) can be effective for heating and driving… (More)
The high-β operating regime of spherical tori (ST), such as in the National Spherical Torus Experiment (NSTX) and the Mega Amp Spherical Tokamak (MAST), makes them attractive fusion devices. For access to such high β regimes it is necessary to heat and to drive currents in ST plasmas. In the electron cyclotron range of frequencies such plasmas are overdense… (More)
Coupled theoretical and computational work is presented aimed at understanding and modeling stimulated Raman backscattering (SRBS) relevant to laser-plasma interactions (LPIs) in large-scale, nearly homogeneous plasmas. With the aid of a new code for simulating and studying the nonlinear coupling in space-time of a large number of modes, and a fluid… (More)
This paper studies the coherent acceleration of ions interacting with two electrostatic waves in a uniform magnetic field B 0. It generalizes an earlier analysis of waves propagating perpendicularly to B 0 to include the effect of wavenumbers along B 0. The Lie transformation technique is used to develop a perturbation theory describing the ion motion, and… (More)
Introduction The work of this group is concerned with phenomena relevant to controlled fusion energy generation in high-temperature plasmas that are confined magnetically or inertially, and phenomena in space plasmas. We report on five studies of the past year.
From properties of wave energy flow conservation and wave energy flow under time reversal, we derive the symmetries in dissipation-free mode conversion in an inhomogeneous plasma. These are applied to high-temperature plasma mode conversions near the ion-ion hybrid and upper hybrid resonances .
The conventional ordinary and extraordinary modes in the electron cyclotron range of frequencies are not suitable for heating of and/or driving currents in spherical tori (ST) plasmas. However, electron Bernstein waves offer an attractive possibility for heating and current drive in this range of frequencies. In this paper, we summarize our theoretical and… (More)
The spatial topology of magnetic field lines can be chaotic for fields generated by simple current configurations. This is illustrated for a system consisting of a circular current loop and a straight current wire. An asymmetric configuration of the current system leads to three-dimensional spatially chaotic magnetic fields. The motion of charged particles… (More)
The excitation and localized damping of electron Bernstein waves EBW in toroidally connned plasmas presents the possibility of eecient means for plasma heating, current drive, and current proole control with external power in the electron cyclotron range of frequencies ECRF. Such use of EBW is particularly interesting for high-plasmas e.g., START, MAST,… (More)