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P: Fachverband Plasmaphysik

P 22: Theorie/Modellierung II

P 22.2: Vortrag

Donnerstag, 2. April 2009, 12:35–12:50, HS Biochemie (groß)

The saturation of the electron beam filamentation instability by the self-generated magnetic field and magnetic pressure gradient-driven electric field — •Mark Eric Dieckmann^1,2, George Rowlands³, Ioannis Kourakis⁴, and Marco Borghesi⁴ — ¹Department of Science and Technology, Linköping University, Sweden — ²Institut fuer Theoretische Physik IV, Ruhr-Universität Bochum — ³Physics Department, Warwick University, U.K. — ⁴Centre for Plasma Physics, Queen's University Belfast, U.K.

Two counter-propagating cool and equally dense electron beams are modelled with PIC simulations. The filamentation instability is examined in one spatial dimension. The box length resolves one pair of current filaments. It is demonstrated, that the force on the electrons imposed by the electrostatic field, which develops during the nonlinear stage of the instability, oscillates around a mean value that equals the magnetic pressure gradient force. The forces acting on the electrons due to the electrostatic and the magnetic field have a similar strength. The electrostatic field reduces the confining force close to the stable equilibrium of each filament and increases it farther away. The confining potential is not sinusoidal, and it permits an overlap of current filaments with an opposite flow direction. The scaling of the saturation amplitude of the magnetic field with the filament size differs from that expected from the magnetic trapping model. The latter nevertheless gives a good estimate for the magnetic saturation amplitude.