VISCOUS TRANSPORT TO THERMAL EQUILIBRIUM
(Rigid Rotation)

Research Activity on Transport

On this page we discuss the work on bulk particle transport done on the EV apparatus. From measurements of the plasma transport we experimentally determine the coefficient of viscosity in our pure electron plasma.

We measure bulk particle transport toward the thermal equilibrium state of rigid rotation, i.e. w(r)=constant, where w is the TOTAL fluid rotation frequency (ExB part + diamagnetic part).

When external torques (due to neutrals and field errors) are made negligible, particle transport is found to conserve total angular momentum and depend upon the shear in the TOTAL fluid velocity, indicating a viscous-like internal transport mechanism.

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Abstract of Poster presented by Jason Kriesel at the 1999 Non-Neutral Plasmas Workshop in Princeton, NJ:

Viscous transport in pure-electron plasmas is a rearrangement of particles due to like-particle interactions, eventually leading to a confined global thermal equilibrium state. The measured transport is observed to be proportional to the shear in the total (ExB + diamagnetic) fluid rotation of the plasma, for both hollow and monotonic rotation profiles. We determine the local kinematic viscosity, (kappa), from measurements of the local flux of electrons. The measured viscosity is 50-10,000 times larger than expected from classical transport due to short-range velocity-scattering collisions, but is within a factor of 10 of recent theories by O'Neil and Dubin of transport due to long-range drift collisions. The measured viscosity scales with magnetic field and plasma length roughly as B/L. This scaling suggests a finite-length transport enhancement caused by particles interacting multiple times as they bounce axially between the ends of the plasma.

PDF Version of Proceedings Paper

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