Thermionic Emission from Hot Particles in a Plasma

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Abstract
Some plasmas contain condensed species as liquid or solid particles which may be hot enough to emit electrons thermionically into the plasma. The charge and voltage distributions in the vicinity of the particle are determined from the Poisson—Boltzmann equation and from a plasma sheath theory that is modified to account for thermionic emission. There is a critical temperature T0 at which the sheath changes from an ion sheath to an electron sheath. At temperatures greater than T0 an electron cloud is injected into the plasma, but it is confined near the particle surface within a distance less than the Debye shielding distance. Some typical voltage and charge density profiles are given for a rocket exhaust plasma.