Geodesic Acoustic Modes (GAM) are known to constitute a continuous spectrum due to radial inhomogeneities. The existence of a singular layer causes GAM to mode convert to short wavelength kinetic GAM (KGAM) via finite ion Larmor radius (FLR) and finite guiding-center drift-orbit-width (FOW) effects. The dispersion relation of GAM/KGAM with FLR/FOW as well as parallel electric field contribution...

The physics of a locked magnetic island chain maintained in the pedestal of an H-mode tokamak plasma by a static, externally generated, multi-harmonic, helical magnetic perturbation is investigated. The non-resonant harmonics of the external perturbation are assumed to give rise to significant toroidal flow damping in the pedestal, in addition to the naturally occurring poloidal flow damping. F...

The physics of a locked magnetic island chain maintained in the pedestal of an H-mode tokamak plasma by a static, externally generated, multi-harmonic, helical magnetic perturbation is investigated. The non-resonant harmonics of the external perturbation are assumed to give rise to significant toroidal flow damping in the pedestal, in addition to the naturally occurring poloidal flow damping. F...

Three-wave nonlinear coupling among spatial Fourier modes of density and magnetic fluctuations is directly measured in a magnetically confined toroidal plasma. Density fluctuations are observed to gain (lose) energy from (to) either equilibrium or fluctuating fields depending on the mode number. Experiments indicate that nonlinear interactions alter the phase relation between density and magnet...

This paper reports ductile or partial ductile mode machining of silicon, glass and some advanced ceramics. Results are presented using scanning electron micrographs of the machined surfaces. Grinding and lapping operations using inexpensive machine tools could produce ductile streaks on surfaces of these brittle materials under good conditions. Manufacture of spherical glass lenses by the fract...

Experiments have been carried out on the EXTRAP T2R reversed-field pinch device to study several important issues related to feedback control of resistive wall modes (RWMs). The feedback system includes a sensor coil array, a feedback controller implementing a feedback law and an active coil array. The issues include 1) effects of sideband harmonics produced by the feedback system, 2) the form ...