Ecton processes in pulsed high-current electron beams

Abstract

Summary form only given. Pulsed high-current electron beams are known to be produced by initiating explosive electron emission. This type of emission takes place when an energy exceeding the sublimation energy of the cathode material has been concentrated in a cathode microvolume within a short time. The overheating of the material in the microvolume leads to a microexplosion followed by thermal electron emission giving rise to a bunch of electrons, which we have named an ecton. Each ecton contains 10/sup 11/-10/sup 12/ electrons. The energy responsible for the appearance of an ecton approximates 10/sup -8/ J. The ecton lifetime is 10/sup -9/-10/sup -8/ for many metals. The interrupted character of explosive electron emission is accounted for by the self-cooling of the emission zone due to heat conduction and a decrease in current density. Ectons can be detected by passing the current of explosive electron emission through a small hole of radius /spl Lt/ 1 mm made in the anode. In doing this, the total explosive emission current, which generally increases gradually, changes to a current showing a great number of spontaneous bursts of duration <10/sup -8/ s. Investigations of the ion erosion of cathodes, the ejection of drops, the electron beams produced, etc. Have allowed a comprehensive study of the properties of ectons. Thus, we have demonstrated that a high-current electron beam produced through explosive electron emission consists of a great number of short-living microbeams and ectons. The ecton structure of this type of beam may affect its properties, namely, the current density distribution over the beam cross section, the uniformity of the electron emission from the cathode, the temporal uniformity of the beam, etc.