Roswell Lee

Nonphysical self forces in some electromagnetic plasma-simulation algorithms

Abstract : The paper describes a simple algorithm for removing nonphysical self forces from two popular electromagnetic plasma simulation models. This algorithm also has two additional features; it considerably reduces short-wavelength noise and unwanted numerical fluctuations, and permits faster integration of the particle orbit equations by roughly a factor of two.

Time‐dependent impedance behavior of low‐impedance REB diodes during self‐pinching

The time‐dependent impedance behavior of large‐aspect‐ratio pinched electron‐beam diodes with no external magnetic field is investigated using two pulsers having 0.4–1.0 MV voltage, and the experimental results are compared to predictions from a time‐dependent computer code which incorporates several important mechanisms that affect diode impedance. A discussion of these mechanisms includes experimental evidence of their existence and their effects on the observed diode impedance. A simple model for the current is used in a time‐dependent analysis of the data in order to demonstrate qualitative effects. The rise time of the electric field, the cathode‐plasma velocity, the time‐dependent generation of ion sources from the anode, and the special diode geometries (tapered cathodes) are shown to affect the diode impedance in good agreement with theory.