Ferroelectric Cathode for Producing an Electron Beam Modulated at GHz Frequencies

The ferroelectric cathode is a novel cathode which can emit high density, high quality electron beams. We propose to demonstrate, for the first time, high frequency modulation of a ferroelectric cathode using electronic gating pulses. Fast gating of the ferroelectric cathode has been previously demonstrated on nanosecond time scale with laser pulse gating but such gating is less useful than electronic gating for most applications. The ferroelectric cathode attractive for applications in vacuum electron devices such as microwave tubes and switches because it produces high density, high quality electron beams yet it is inexpensive and operates at room temperature and in poor vacuum. Electron beam emission occurs when an applied gate pulse alters the spontaneous polarization field in the ferroelectric medium. In Phase I, we will design, fabricate and test a ferroelectric cathode capable of operation at a modulation frequency of at least 100 MHz. The electron emission will be tested as a function of gate pulse risetime and anode-cathode gap voltage. An electron gun capable of operation at frequencies in excess of 1 GHz will be designed in Phase I and will be built and tested during the Phase II effort. The ferroelectric cathode is an attractive source for high frequency RF and microwave vacuum electron devices which require high quality electron beams for power and high efficiency operation.