The role of multielectrode geometry in the generation of pulsed intense electron beams in preionization-controlled open-ended hollow-cathode transient discharges

Abstract

High-voltage hollow-cathode glow discharges are used more and more to generate intense, pulsed electron beams. Such intense electron beams can be produced with high efficiency in preionization-controlled open-ended hollow-cathode transient discharges (PCOHC). This novel discharge is initiated by a low-current dc preionization discharge. The beam parameters are similar to those of the electron beam generated in pseudospark discharges. In this work, we present some measurements of the parameters for the electron beam generated by using a multielectrode (multigap) system instead of the single-gap device in this PCOHC configuration. This kind of multielectrode device was already used in pseudosparks to improve the intensity and collimation of the extracted beam. By using the multigap instead of the single gap, the total beam current (100-120 A) and the energetic part of the beam current (peak current 60-90 A and electron energies higher than approximately 3 keV) were substantially increased. However, the energy spectrum of the fast component has a large fraction of electrons at lower energies (4-10 keV for 26 kV breakdown voltage) when a multigap device is used instead of the single-gap configuration. A comparison between the single-gap and multigap PCOHC-produced pulsed intense electron beam is made too. The differences between the high-power pulsed electron beams produced in single-gap and multigap PCOHC configurations seem to be due to different developments of beam generation phases.