Insulation of a hollow beam gun

The authors are investigating the possibility of accelerating particles with a high gradient in a wake-field transformer. They focus on the short-pulse, high-current hollow-beam gun being developed for this experiment and especially on the insulation problems. A laser-driven gun that works in a solenoid field of 0.2 T was chosen. At a cathode voltage of 100 kV, the gun produces a hollow beam of 109-cm diameter with a space-charge-limited current of 100 A over a pulse length of a few nanoseconds. The cathode voltage is limited by vacuum breakdown, caused by electrons, emitted from the cathode and from the surfaces of optical elements between the electrodes.<
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