Low-frequency instability in systems with extraction of electrons from a plasma penetrating into vacuum

Theoretical and experimental study was made on stability of operation of electron source with electron extraction from a plasma penetraiting into vacuum. It is shown, that low-frequency instability, occurring due to formation of colliding flux of ions, reflected from electron extractor, developes in such systems. Oscillation frequencies are determined by the time of ion flight through potential well, formed when electron extracting from penetrating plasma. The modulation depth of extracted electron flux achieves 50%