Ion heating in the presheath
Date
2007-03-19
Authors
Meige, Albert
Sutherland, Orson
Smith, Helen B.
Boswell, Rod W.
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American Institute of Physics (AIP)
Abstract
A one-dimensional model of a small plasma ion source (10cm long) is studied. A hybrid simulation where ions are treated as particles and electrons as a fluid obeying the Boltzmann relation is used to investigate ion heating in the plasma presheath. At low pressure (below a few mTorr), the ion velocity distribution is Maxwellian in the bulk and becomes a drifting Maxwellian distribution while transiting the presheath. The distribution remains essentially isotropic as the ions are accelerated through the presheath to satisfy the Bohm criterion. At intermediate pressures (around 10mTorr), ion-neutral collisions scatter a significant part of the ion kinetic energy from the parallel direction to the perpendicular direction, leading to a net heating of the ions. In addition, the ion velocity distribution becomes distinctly anisotropic. At higher pressure (above a few tens of mTorr), ion heating is still observed, but yields isotropic ion velocity distributions.
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Keywords: Computer simulation; Elementary particles; Heating; Kinetic energy; Light scattering; Plasma sheaths; Boltzmann relation; Intermediate pressures; Ion velocity distribution; Plasma ion source; Ions
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Physics of Plasmas
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Journal article
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