Thermionic Emission in a Planar Diode

Application ID: 42551

When electrons are emitted from a heated cathode in a plane parallel vacuum diode, they contribute to the space charge density in the diode, which in turn affects the electric potential distribution. If the potential difference between the cathode and the anode is not sufficiently large, a potential minimum forms between them, repelling electrons of insufficient energy back toward the cathode. Such a diode is said to be operating in the space charge limited regime.

In this benchmark model, the dedicated Thermionic Emission feature is used to release thermal electrons from a cathode of a specified temperature and work function. The electron trajectories are bidirectionally coupled to the electric potential calculation in the diode using the specialized Electric Particle Field Interaction multiphysics coupling and Bidirectionally Coupled Particle Tracing study step. The electric potential distribution and the anode current compare favorably to the results of the analytical Langmuir-Fry model.

This model example illustrates applications of this type that would nominally be built using the following products:

Particle Tracing Module