Kinetic and global model simulation for pseudospark discharge

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:213035

Lee, Jae Koo; June, Hae; Lee, Y.Y. Lim ^[1]

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1. Pohang Univ. of Science and Technology (Korea, Democratic People`s Republic of); and others

In the pseudospark discharge with a hollow cathode, good quality high current beams are produced by secondary electrons emitted from the wall as well as by back- scattered electrons and by accelerated ions. This discharge occurs in the low (pd) regime in the Paschen breakdown curve, which is the subject of our studies with a particle-in-cell simulation and a global model which is a time-dependent, volume-averaged zero-dimensional model using the Godyak`s loss formulas. For the former simulation, we employed the kinetic simulation codes, PDP-1 and XOOPIC. For the latter simulation, we formulated time-varying electron and ion density equations and power equation with secondary electron effect in the closed hollow cathode and calculated the electron density and the beam current. It is assumed that a pulse-type power and a cosine-type wall potential whose period is four times of the pulse period are on during the pulse-on time and off during the pulse-off time. In experiments, the discharge current and wall potential oscillate with damping like an L-R-C circuit, but we consider the first one-step of this damped harmonic oscillation. The variation of electron density with various values of the secondary emission coefficient(gamma) is calculated. In this paper the evolution of current density is shown for three different breakdown voltages in the 3-gap case and compared with the experimental current densities shown as the horizontal lines. Also shown is the comparison of experimental data with simulation values at 75 nsec. In this paper various simulation results with different pulse times are shown, which indicates the optimum value of approximately 7 nsec, close to the experimental value of 15 nsec. With some power factor, which is the ratio of the energy delivered to the system during the pulse-on time to the total energy stored in the external capacitor, the simulation results compare well with the experimental data.

• OSTI ID: 213035
• Report Number(s): CONF-950749--
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BEAM CURRENTS
ELECTRIC DISCHARGES
ELECTRON DENSITY
HOLLOW CATHODES
PLASMA SIMULATION
SECONDARY EMISSION