Non-Maxwellian Electron Distribution Functions in Z-Pinch Plasmas
Abstract
The heating and cooling a a z-pinch electron distribution is studied using the Fokker Planck equation. Included in the analysis are the usual Fokker Planck term for distant small-angle electron-electron collisions, a semi- empirical term representing inelastic charge-conserving collisions, ohmic heating by the electric field acting on the current, and compressional heating or cooling. Ions are represented as heavy, highly-charged Maxwellian particles, and electron-ion collisions are given in terms of a Coulomb collision frequency. In deriving the Fokker Planck equation, a first-order Cartesian tensor expansion is performed in a local coordinate system which is spatially uniform and moving with the fluid. The first-order (vector) term in the expansion is assumed to equilibrate much faster than the zero-order (scalar) term. Under some conditions, the electron distribution function has an analytic self-similar solution. A numerical time-dependent solution is also obtained, through an implicit finite-differencing scheme. Advantages of a time-dependent model are noted. The behavior of the electron distribution function and conductivity are demonstrated for different parameters. Production of runaway electrons with perpendicular electric and magnetic fields is discussed. Keywords: Z pinch dynamics; Kinetic theory; Conductivity; Non equilibrium distributions; Runaway electrons.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 27, 1990
- Accession Number
- ADA224702
Entities
People
- K. G. Whitney
- P. E. Pulsifer
Organizations
- United States Naval Research Laboratory