Development of compact high-voltage electronic vacuum devices

The issues of improvement of hold-off capability and reliability of high-voltage vacuum tubes, for example, X-ray tubes were studied. Two methods are suggested for improvement of the tubes operation. The first method is based on deposition of special coatings on the inner surface of tube isolator in the regions where electric field strength is high. These coatings have bulk electric conductivity higher than for isolator material but their surface conductivity is almost equal. The second method is based on pulsed surface melting of the tube electrodes with non-relativistic, high-current electron beam. Pulsed surface melting drastically reduces parasitic field emission, which results in the decrease of the charge density both in the bulk and surface of isolator providing high hold-off voltages through the tube. The tests of 160-kV and 250-kV X-ray tubes made utilizing the new above mentioned technologies have shown that parasitic currents do not exceed 1 μA and conditioning time decreases from 5 hours to 15 minutes. The new technology also allows to reduce dimensions of the tube.