Generation and characteristics of high power long pulse electron beam (propagation in vacuum within different pressure)

For investigation of propagation dynamic of high power long pulse (0, 3–1 ms) electron beam in vacuum within pressure 5∗10⁻⁵ ÷10 Torr two experimental installation were constructed: 1. Electron energy − 300 keV, current 30–100 A, pulse 0,35 ms long; 2. Electron energy 500–600 keV, current 30–200 A, pulse 1 ms long. Two different macroinstabilities of the beam have been observed. One of them had freaquences up to 10 MHz within pressure 5∗10⁻⁵ ÷1 Torr. Second had freaquences several kiloherzes within pressure 5∗10⁻⁵ ÷10 Torr. When pressure was 5∗10⁻⁵ ÷5∗10⁻⁴ Torr monotonous increasing of beam diameter along transport way was observed depending on beam microinstability.