Damage to ferroelectic cathodes from surface discharge and mechanical strain

Summary form only given. High power microwave devices require electron sources with high current densities (1-5 kA/cm/sup 2/) which have constant emission properties over a long pulse duration (0.5-1.0 /spl mu/s). Typically explosive emission cathodes are used, however these sources produce plasma along with the electron beam which interferes with the beam shape and contributes to gap closure. Ferroelectric ceramic materials are currently being investigated as an alternate source. To achieve electron emission from these materials it is necessary to create a charge imbalance at the surface rapidly altering the polarization which is usually done with a pulsed electric field. The conditions of the experiment also create a triple point at the metal-vacuum-dielectric interface at which the intensity of the electric field may be several orders of magnitude higher than the bulk electric field. This enhancement can cause a plasma discharge at the edge of the grid. Damage to the grid from this phenomenon has been documented using a scanning electron microscope.