Using of pulse high-voltage dielectric flashover for formation of REB with super-short front for high-power MW generators

Existing high-power accelerators could not generate relativistic electron beams (REB) with the required parameters as follows: 1-2 MeV, 10-20 kA, 200-300 ns and, at the same time, with the front rise time of the order of or less 1 ns. It is determined by the physical restrictions in the vacuum insulator of a diode of a high-power accelerator. In view of this fact, final front shortening has to take place in the vacuum part of the high-voltage diode. It needs a very fast switch for REB commutation. From the point of view of simplicity, use of dielectric flashover as a very fast and stable process is put in perspective for this purpose. One attempt in this direction was made by the Moscow Radiotechnical Institute by using of the electromagnetic shock wave formation phenomenon taking place in the cathode line with a sufficiently long dielectric insert. REB's front shortening from 10-15 ns up to a value of 1-1.5 ns has obtained experimentally. So a kind of REB could not be used directly in usual high-power MW generators with an external magnetic field. For this reason, the authors suggest the use of a two-beams cathode as a source of the REB with very short front duration (1 ns or less). For this purpose, the secondary beam is delayed for the front duration of the primary beam by means of some dielectric surface discharger. The primary beam is captured by a collector and the secondary is utilized in a MW generator. In this report, the authors show the theoretical ground in detail and discuss an experimental verification of this idea.