KILOAMPERE AND MICROSECOND ELECTRON-BEAMS FROM FERROELECTRIC CATHODES

We report experimental results of the operation of two ferroelectric c athodes of relatively large size. The first cathode had a diameter of 10.2 cm and was built in the Pierce cathode geometry by Integrated App lied Physics (IAP). It achieved emission currents of up to 1.2 kA (15. 3 A/cm(2)) at voltages up to 100 kV, in 150 ns pulses. The second cath ode had an annular shape with a diameter of 11.4 cm and a width of 0.2 5 cm. It was built at the Massachusetts Institute of Technology to pro duce an annular electron beam for use in a Gyrotron microwave source. It operated at currents of up to 10 A (1.1 A/cm(2)) at 8 kV, in 5 mu s pulses. Detailed operating characteristics for each of these electron sources are reported. These results indicate that ferroelectric catho des can be used to produce electron beams of large area and size, with high total operating current and pulse lengths of several microsecond s. These sources should be suitable for use in future microwave genera tion experiments.