The influence of a change in the electron trajectory in the vacuum-diode anode–cathode gap on the impedance

Abstract

The analysis of the influence of the electron-trajectory curvature in the anode–cathode gap of a vacuum diode on its impedance during generation of high-current electron beams is performed, and the applicability of the one-dimensional Child–Langmuir formula for the electron-current calculation is evaluated. The results of an experimental study of a flat diode with explosive-emission graphite, copper, and carbon- fabric cathodes and also with a multipointed cathode are presented. These investigations were performed on the TEU-500 accelerator (350–500 kV, 60 ns). A strip diode with a graphite cathode was also studied in the mode of magnetic self-insulation of electrons. The experiments were performed on the TEMP-4М accelerators (150–200 kV, 400–600 ns). The investigation results showed that the satisfactory coincidence of the experimental values of the total current with those calculated from the one-dimensional Child–Langmuir formula (for the working area of the cathode) is observed in diodes not only in the absence of a change in the electron trajectory in the anode–cathode gap but also upon a deflection of the trajectory from the normal to the cathode surface by an angle of <90°. An increase in the electron current owing to a decrease in the anode–cathode gap and an increase in the emission area of the cathode during the cathode-plasma production and also at the expense of the presence of microirregularities on the cathode is properly described by the onedimensional Child-Langmuir formula, if the above factors are taken into account.