High Current Ferroelectric Cathode Without A-K Gap Closure

Electron sources with high emission current densities capable of operating in poor vacuum with A-K gap closure are required by electron beam experiments. Thermionic cathodes and field emission cathodes are limited by current density, high vacuum and high field requirement or degradation of vacuum when operated repetitively. We propose to design, build, and test a high current, high voltage ferroelectric cathode for microsecond pulse operation without A-K gap closure. Ferroelectric cathodes operate at room temperature using spontaneously polarized materials such as Pb(Zr,Ti)O3. Previous research at CERN, Cornell, and Integrated Applied Physics has demonstrated these cathodes to be sources of high current density, high quality electron beams. Emission of microsecond pulses has been observed. Previous research has also indicated good electron gun performance using the ferroelectric cathode at poor vacuum (~10^-3 Torr) without poisoning or A-K gap closure. During Phase I, we will demonstrate electron gun operation producing a beam of 5 cm radius up to 150 kV and 5kA, and test ferroelectric cathodes of different material compositions. Based on the Phase I work, an advanced cathode can be designed, built, and tested during Phase II to operate at 500 kV in microsecond pulses at high repetition rates.