The polarity dependent effect of gyroviscosity on the flow shear stabilized RayleighTaylor instability
Abstract
The linear dispersion relation is reviewed for perturbations of an incompressible finite Larmor radius plasma with an equilibrium density and horizontal fluid velocity varying with depth in a uniform gravitational field. The velocity and magnetic field are assumed to be parallel and transverse to the wavenumber, respectively. Stability criteria are derived for piecewise uniform cases representing a magnetically accelerated plasma layer with sheared flow. High wavenumber stability differs significantly if the direction of the magnetic field is reversed, with gyroviscosity being either stabilizing or destabilizing depending on direction. This is consistent with a plasma focus's observed preference for a central anode. For a given current waveform and a central anode, a maximum value for the product of the driving magnetic field magnitude and risetime is derived for high wavenumber stability. When combined with a recognized empirical scaling law for neutron yield optimized D_{2} plasma foci, a maximum current is implied. For a linearly rising current, for example, this is 4 MA. Strategies for mitigating the constraints are discussed.
 Publication:

APS Division of Plasma Physics Meeting Abstracts
 Pub Date:
 October 2003
 Bibcode:
 2003APS..DPPUO2014R