Kiloampere and microsecond electron beams from ferroelectric cathodes

We report experimental results of the operation of two ferroelectric cathodes of relatively large size. The first cathode had a diameter of 10.2 cm and was built in the Pierce cathode geometry by Integrated Applied Physics (IAP). It achieved emission currents of up to 1.2 kA (15.3 A/cm/sup 2/) at voltages up to 100 kV, in 150 ns pulses. The second cathode had an annular shape with a diameter of 11.4 cm and a width of 0.25 cm. It was built at the Massachusetts Institute of Technology to produce an annular electron beam for use in a Gyrotron microwave source. It operated at currents of up to 10 A (1.1 A/cm/sup 2/) at 8 kV, in 5 /spl mu/s pulses. Detailed operating characteristics for each of these electron sources are reported. These results indicate that ferroelectric cathodes can be used to produce electron beams of large area and size, with high total operating current and pulse lengths of several microseconds. These sources should be suitable for use in future microwave generation experiments.