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Trapped-Ion Current Enhancement Beyond the Space Charge Limit in Plasma Cathodes

A first-principles model of how positive ions trapped in the virtual-cathode potential well of a plasma-facing thermionic cathode raise the transmitted electron current above the traditional space-charge limit. Students learn how the trapped-ion plasma forms a quasineutral region that shifts the marginal space-charge-limited emission surface outward, and how the balance between charge-exchange ion creation and ion leakage sets the well voltage and the achievable current.

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Thermionic Current Beyond the Traditional Space Charge Limit Enabled by Trapped Ions in the Virtual

We show that ion trapping in virtual cathodes can raise the transmitted current of emitted electrons much closer to the full emission than is predicted by theories without trapped ions. The transmitt…