Operation of ceramic cathodes with bipolar pulse excitation

The emission from ferroelectric cathodes excited by bipolar pulses does not suffer the hysteretic behavior shown with monopolar pulse excitation. This is because the bipolar pulse forces a neat charging-discharging cycle of t he whole surface of the sample, and, therefore, the flipping of the polariz ation. The emission becomes definitely stable, whereas it was erratic in cu rrent amplitude, pulse shape and starting time with monopolar excitation. T he emission yield of energetic electrons from ferroelectric cathodes of dop ed lead-titanate-zirconate-lanthanum increased from a few hundreds of milli amperes to some amperes (with current density of 30-50 A/cm(2)) in passing from monopolar to bipolar voltage pulse excitation. (C) 2001 American Insti tute of Physics.