Modeling of diode emission processes

The formation and evolution of cathode and anode plasmas in high power vacuum diodes is important for many reasons. For fast response diodes rapid plasma formation is essential, while for long pulse operation, plasma motion has detrimental effects on diode impedance. In the production of high quality electron and ion beams the plasma motion also influences beam optics. Finally, the plasma evolution may affect the stability of the diode power flow. In this paper, a model of the cold-cathode emission of a non-ideal vacuum diode is presented. This model is the basis for a new computer code DIODE which considers the plasma formation and chemistry in an attempt to understand the implications of surface coatings and/or the surface absorption of various materials. The code models the initial formation of a cathode plasma starting from the localized vaporization of the cathode and then models the coupled hydrodynamic expansion of the plasma.