Space-Charge Effects in the Current-Filamentation or Weibel Instability

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M. Tzoufras,¹ C. Ren,² F. S. Tsung,³ J. W. Tonge,³ W. B. Mori,^1,3 M. Fiore,⁴ R. A. Fonseca,⁴ and L. O. Silva⁴
¹Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA
²Departments of Mechanical Engineering and Physics and Astronomy, University of Rochester, Rochester, New York 14623, USA and Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA
³Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
⁴GoLP/Centro de Fisica dos Plasmas, Instituto Superior Tecnico, 1049-001 Lisboa, Portugal

Received 13 October 2005; published 15 March 2006

Weconsider how an unmagnetized plasma responds to an incoming fluxof energetic electrons. We assume a return current is presentand allow for the incoming electrons to have a differenttransverse temperature than the return current. To analyze this configurationwe present a nonrelativistic theory of the current-filamentation or Weibelinstability for rigorously current-neutral and nonseparable distribution functions, f₀(p_x,p_y,p_z) [not-equal] f_x(p_x)f_y(p_y)f_z(p_z). Wefind that such distribution functions lead to lower growth ratesbecause of space-charge forces that arise when the forward-going electronspinch to a lesser degree than the colder, backward-flowing electrons.We verify the growth rate, range of unstable wave numbers,and the formation of the density filaments using particle-in-cell simulations.

URL:	http://link.aps.org/doi/10.1103/PhysRevLett.96.105002
DOI:	10.1103/PhysRevLett.96.105002
PACS:	52.35.Qz; 52.35.Hr; 52.57.Kk 52.35.Qz Plasma microinstabilities including ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron instabilities, etc 52.35.Hr Plasma electromagnetic waves electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid waves 52.57.Kk Fast laser ignition of compressed fusion fuels YEAR: 2006
KEYWORDS:	plasma instability, space charge, plasma temperature, plasma transport processes, plasma simulation, plasma density