Experimental Investigation on Temporal Evolution of Beam Plasma Discharge

A pulse (∼200 µs) of electron beam (0.3∼1.5 kV, 2∼20 mA) is injected into Argon gas (10-5∼10-4 Torr) in a magnetic field (50∼300 G). A two-stream instability develops from low frequency (∼MHz) to high frequency (∼100 MHz) in proportion to the increase of the plasma frequency. When the instability frequency reaches the cyclotron frequency, the wave energy is rapidly transferred by cyclotron damping to the plasma and an ionization avalanche (beam plasma discharge) occurs.