Space-charge effects in the field-assisted thermionic emission from nonuniform cathodes

Abstract

We use computational simulations to study the electron emission and propagation in planar vacuum diodes. We show how space-charge affects thermionic emission from cathodes with two different values of work function that form a checkerboard pattern of finite extent on the cathode surface. We confirm that, for intermediate cathode temperature, the local current density from low work function regions can exceed the space-charge limit for the entire cathode. As the cathode temperature rises space-charge effects lead to homogeneous current density from the interior of the emitting area and a higher current density from its periphery. We show how beam emittance and brightness are affected, and show that the operating temperature for optimal brightness is such that it corresponds to the transition region between source-limited and space-charge limited emission. Finally we show how beam current and beam quality depend on how fine grained the structure of the cathode is.

arXiv comment7 pages, 9 figures

References in corpus (3)

• Molecular Dynamics Simulations of Field Emission From a Planar Nanodiode
• Synchronization in arrays of vacuum microdiodes
• Molecular Dynamics Simulations of Mutual Space-Charge Effect between Planar Field Emitters

Cited by in corpus (6)

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• Physical factors governing the shape of the Miram curve knee in thermionic emission
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• Discrete Electron Emission
• Charge transport and mode transition in dual-energy electron beam diodes