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Collisionless and collisional effects on plasma waves from a partition squeeze

Published online by Cambridge University Press:  24 November 2014

Arash Ashourvan*
Affiliation:
Department of Physics, U.C. San Diego, La Jolla, CA 92093
Daniel H. E. Dubin
Affiliation:
Department of Physics, U.C. San Diego, La Jolla, CA 92093
*
Email address for correspondence: [email protected]

Abstract

A simple 1D model is presented for the heating caused by cylindrically-symmetric plasma waves in a non-neutral plasma column due to the addition of a symmetric squeeze potential applied to the center of the column. We study this model by using analytical techniques and by using a numerical grids method solution, and we compare the results of this model to previous work (Ashourvan and Dubin (2014)). squeeze divides the plasma into passing and trapped particles; the latter cannot pass over the squeeze potential. In collisionless theory, enhanced heating is caused by additional bounce harmonics induced by the squeeze in the particle distribution, leading to Landau resonances at energies En for which the bounce frequency ωb(E) and wave frequency ωm satisfy ωm = nωb(En). As a result, heating is substantially higher than the case with no squeeze, even when ωm is much greater than the thermal bounce frequency ωb(T). Adding collisions to the theory creates a boundary layer at the separatrix between trapped and passing particles that further enhances the heating at small ωm/kmvs, where km is the axial wavenumber and vs is the velocity at the separatrix. However, at large ωm/vs, the heating from the separatrix boundary layer is only a small correction to the heating from collisionless resonances in the trapped particle distribution function.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2014 

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