Emission properties of metal-ceramic, velvet, and carbon fiber cathodes

We present results of studies of emission properties of cathodes at accelerating fields of 3 – 6×10⁴ V/cm. We investigated cathodes which are made of metal-ceramic, carbon fibers, carbon fabric, velvet or corduroy. Experimental data concerning light emission from the cathode surface, uniformity and divergence of the generated electron beams are presented. Data related to the impedance, power, and energy of diodes operating with these cathodes are given as well. It was found that the tested cathodes, except the cathode made of carbon fibers, showed significant degradation of their emission properties within 4×10³ generator shots. We also present data of the vacuum deterioration as a result of cathode operation.