| THE PIERCE-DIODE AS A MODEL FOR SELFOSCILLATIONS AND CONTROLLING CHAOS IN THERMIONIC DISCHARGES (2007) | |||||||||||||
Abstract | |||||||||||||
| The classical Pierce diode is the simplest model of a collisionless bounded plasma system [1]. It is an one–dimensional electrostatic model consisting of two electrodes with a short circuit, an emitter (x =0) and a collector (x = d). From the emitter a monoenergetic beam of electrons is injected, and is absorbed completely at the collector. The electrons are neutralised by an immobile ion-background of the same density as the electron beam at x =0. The classical Pierce diode can be described by one fluid equation for electron density and electron velocity and the Poisson equation for the electric potential. The stability properties of the Pierce diode are solely dependent on the dimensionless Pierce parameter � = ! peL where! pe = q n0e 2 = � em e is the electron plasma frequency at the emitter, L the lenght of the electrode gap, and v0 the velocity of the monoenergetic electron beam emitted from the collector. In the first part of the present contribution an extensions of this model is presented, which takes into account ion dynamics, collisions with neutrals, and sheath capacitance. The extended Pierce diode can be used to understand the trigger mechanism of selfoscillations of thermionic | |||||||||||||
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