Fracture of electrodes in a three-electrode pulsed X-ray tube with explosive emission
E.I. Palchikov1,2
1Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Science, Novosibirsk, Russia
2Novosibirsk National Research State University, Novosibirsk, Russia
Keywords: explosive emission, fracture, high electric fields in vacuum, ion and electron bombardment
Abstract
Fracture of the electrodes of a three-electrode pulsed X-ray tube with a rechargeable insulated electrode operating in explosive emission mode at a voltage of 600 kV and pulsed current up to 1000 A was investigated. The fracture was produced by the action of high pulsed electric fields and pulsed flows of electrons and plasma during vacuum breakdown in X-ray tubes. X-ray fluorescence microanalysis using a scanning microscope revealed the presence of numerous metal globules of size 10÷40 mu formed from both the tungsten anode material and the material of the third insulated Kovar electrode. Several stages of separation of the globules by the electric field were detected on the insulated electrode. Quantitative estimates for the critical values of Coulomb forces at which droplets arise were obtained in accordance with a dynamic model (taking into account the kinetic energy accumulated by the mass during the exposure to the electric field and surface energy), and the electric field pressures during the operation of the tube were estimated, allowing an explanation of the observed phenomena.
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