An apparatus for the investigation of ceramic cathodes with relevant results

A ceramic cathode is a disk of typically 10–15 mm diameter, thickness less than 1 mm, with metallic electrodes at the two surfaces. It emits bursts of ⩽2 keV,∼5 A electrons when excited with a ∼2 kV–100 A–200 ns bipolar pulse. Its behavior depends strongly on the pattern of the front electrode, on the dielectric constant of the material, so in turn, on the temperature. The high voltage excitation pulse applied to the electrodes induces the plasma initiation at the triple points and also the polarization of the material. The polarization variation acts on the electrons set in the plasma sheet and, possibly, on the sample surface generating pulses of energetic electrons. The excitation voltage pulse, the displacement current and the emitted current are recorded for studying the physics of the emission phenomenon. The procedure of the material growth and the tests of its relevant properties are presented.