Potential Formation Due to Contact betweenFloated Emissive Electrode and Plasma

Abstract

Potential formation due to contact between a floated emissive plane electrode and collisionless plasma is investigated by means of particle simulations. When low-temperature high-density thermal electrons are emitted, a negative potential dip is created in front of the electrode. With an increase in the emission flux from the electrode, the electrode potential increases and finally becomes larger than the plasma potential. When a high-density electron beam is injected from the floated electrode, there appears a stationary electron sheath in front of the electrode, which reflects most of the injected electrons. This sheath also reflects ions flowing from the plasma toward the electrode. When the beam density is low, such an electron sheath is not created. An intermediate-density beam injection gives rise to a recurrence phenomenon and the electron sheath structure appears periodically in time.