Low frequency instability excited by a partially neutralized relativistic electron beam

The propagation of a nu / gamma =0.16 relativistic electron beam of 150 ns pulse length is found to be inhibited when the beam is injected into a drift tube filled with hydrogen gas of approximately=1 Pa pressure. The beam and plasma ion density then reach values of comparable magnitude during the pulse. Measurements with a floating double probe indicate the presence of an instability situated near the lower hybrid frequency. The observed phenomena are attributed to the ion-resonance instability.