Development of long-lifetime cold cathodes

The paper presents the results of an experimental study of the cold cathodes used in the Sinus-type repetitive high-current accelerators. The accelerating voltage for this accelerator is on a level of 100-1000 keV, the electron beam current is 1-10 kA, the pulse duration is 10-40 ns, and the pulse repetition rate is up to 200 pps. The emissive properties of the cathodes were investigated for both planar and coaxial magnetically insulated vacuum diodes. To produce high-current electron beams in coaxial diodes, a strong magnetic field of strength up to 30 kOe created by a superconducting solenoid was used. Investigated in the experiment were explosive-emission cold cathodes of varied geometry made of various materials such as copper, steel, stainless steel, bronze, graphite, and carbon-graphite cloth as well as metal-dielectric cathodes depending for their operation on an incomplete electrical discharge over the dielectric surface. The longest lifetime has been attained for a metal-dielectric cathode in a planar vacuum diode; it is over 10/sup 8/ shots. The cathode provided the current density at the anode 20-25 A/cm/sup 2/ for the accelerating voltage 600 kV, pulse duration 20 ns, and pulse repetition rate up to 200 pps.