Research Projects
Cold Plasma Particle-Particle Collisions and Self-Heating
*** THIS PROJECT IS NO LONGER ACTIVE ***
Hang-Ping Chen1 and Charles K. (Ned) Birdsall
Using the input file coldplas.inp from our venerable electrostatic periodic Particle-in-Cell (PIC) code XES1 (available at http://ptsg.eecs.berkeley.edu), we observe cold plasma oscillations excited in the fundamental mode [1].
Let two electrons be loaded at x = L/4 and at x = 3L/4 for a system of length L. The ions form a uniform stationary background that makes the periodic system net neutral. The particle excitation at t = 0 is an x-velocity v1 = A sin kx in fundamental mode 1, with amplitude A and kL = 2Π. With small A, the Vx-x phase space shows two ellipses, each centered at the starting positions and with oscillations at the input plasma frequency, as expected. As A is increased, the two particles collide at x = L/2 and reflect. The particle oscillatory and colliding motion histories are observed by tracing their Vx-x motions.
Next, 64 electrons are loaded uniformally in x and excited in the fundamental mode using small A and producing 64 non-colliding elliptical orbits with an envelope in mode 1. When A is increased, the question now becomes "which electrons collide first?" We observe crossing first at x = 0 or at x = L/2 , where neighboring orbits have opposite x-velocities. These collisions randomly scatter the particles, and the field, kinetic, and total energies grow non-physically with time.
DRAFT of submission to ICOPS, as poster paper, with simulation, February 26, 2005.
- [1]
- C. K. Birdsall and A. B. Langdon, Plasma Physics via Computer Simulation, Institute of Physics (IOP), Philadelphia, PA, 1991, Prob. 5-3c, p. 89.
1Mechanical Engineering