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 the whole surface of the sample, and, therefore, the flipping of the polarization. The emission becomes definitely stable, whereas it was erratic in current amplitude, pulse shape and starting time with monopolar excitation. The emission yield of energetic electrons from ferroelectric cathodes of doped lead-titanate-zirconate-lanthanum increased from a few hundreds of milliamperes to some amperes (with current density of 30-50 A/cm(2)) in passing from monopolar to bipolar voltage pulse excitation. (C) 2001 American Institute of Physics.