Electrostatic shocks in plasmas can accelerate particles to twice the shock velocity with a very low energy spread. In this thesis the effects of a weak but finite ion collisionality are considered in a time dependent semi-analytical treatment, which can be of interest for laboratory shocks. With collisons, the amplitude of the downstream potential oscillation is found to increase approximately as the square root of time. This thesis also studies the effect of electron trapping in the potential oscillations downstream of the shockfront. Two model electron distributions, which are flat in the trapped regions of phase-space, are considered. In general the effects of electron trapping are to lower the maximum electrostatic potential, but at the same time increase the range of shock propagation speeds for which electrostatic shock solutions exist. One of the electron trapping models also displays multiple shock solutions for the same temperature ratio and Mach number in certain parameter regions.
Student project presentation
PJ, lecture hall, Fysik Origo, Fysik
19 April, 2018, 14:30
19 April, 2018, 15:30