50 Hz electron emission from PZT ferro-electric cathodes

Summary form only given, as follows. Ferro-electric cathodes may offer a source of high current density electron beams for applications where the use of conventional field emitters is limited by repetition rate and lifetime. In a ferro-electric cathode, electrons are emitted when the spontaneous polarization is rapidly changed by a pulsed electric field applied across the ferroelectric. When no additional voltage is applied to a planar diode gap, emission current densities are on the order of 1 A/cm/sup 2/. When an additional field is applied to the gap, we have measured current densities up to 100 A/cm/sup 2/. In a new configuration that permits beam extraction into a drift tube, the cathode is pulsed 10-20 kV negative and electron current densities of /spl sim/20 A/cm/sup 2/ at repetition rates up to /spl sim/50 Hz (power supply limited) have been measured. The one inch diameter ferro-electric cathode is located in the fringing region of a 1.5 kG solenoid magnetic field /spl sim/2.8 cm from the entrance of a grounded drift tube. A Faraday cup is located several centimeters inside the drift tube and measurements show that repeatable beam current can be extracted from the ferroelectric cathode in this geometry.