Application of Particle Simulations to the NRL Laser Experiment.
Abstract
Particle simulation methods are used to address issues related to recent results of the NRL laser experiment. The simulations, which include all the electron and ion scale lengths, examine dense plasma clouds expanding across a magnetic field into a vacuum under various conditions. The wavenumbers of the observed short wavelength instability, identified as the lower hybrid drift instability, are found to be independent of the magnetic field (in agreement with experiment) and the ion to electron mass ratio, consistent with a simple model for the expansion. In addition, differences in the instability due to the initial velocity distribution and the angular spread of the expansion are studied. Nonlinear phenomena, such as possible flute tip bifurcation, bending and separation, have also been observed in the calculations and are related to similar effects seen in the experiments. However, detailed analysis of the simulations show that there is no short wavelength cutoff to the instability, contrary to the predictions of linear theory, indicating that the wavelength scaling is spurious. Possible physical and numerical reasons for this behavior are examined, and it is shown that another instability, the electron cyclotron drift instability can still be excited at shorter wavelengths. The overall consequences of the results on the suitability of these methods for modeling the laser experiment are discussed. Keywords: Laser experiment, Early time structuring, Particle simulations, Flute instabilities.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 10, 1987
- Accession Number
- ADA191641
Entities
People
- D. Winske
Organizations
- Los Alamos National Laboratory