Emission properties of metal-ceramic and velvet cathodes

Summary form only given. We present a comparison between the parameters of a metal-ceramic cathode and the parameters of a velvet cathode which were studied at the same conditions. The cathodes had an emitting area of 100 cm/sup 2/. Experiments were performed using of PFN generator having the following output parameters: accelerating voltage of 250 keV, impedance of 80 /spl Omega/ and 140 /spl Omega/, and pulse duration of 250 ns and 450 ns at FWHM. The time delay of the electron emission was measured versus the amplitude and rise time of the accelerating voltage. The uniformity of the cathode plasma formation and its expansion towards the anode was studied by a fast framing camera. The electron beam uniformity with spatial and temporal resolution and its micro-divergence was obtained using the X-ray image produced by the electron beam interaction with a Ta-made anode and by a multi pinhole camera, respectively. In addition, array of collimated Faraday cups was used to obtain electron beam uniformity. The changes of the emission properties of the metal-ceramic cathode were studied at a repetition rate of 1 Hz during 10,000 shots of the PFN operation. Compatibility of the cathodes with vacuum requirements is presented.