Propagation studies using modulated relativistic electron beams

The propagation of intense relativistic electron beams in a gas can be hampered by the low-frequency hose instability. Modulating the beam current, however, enhances the stability of the beam in certain pressure regions. These regions are characterized by the basic parameters of beam radius and plasma channel conductivity profile. Techniques unique to the measurement of these and other plasma parameters are reported and new experimental results are presented. These results pertain to a 5-MeV electron beam of 300-nsec duration. The average beam current ranges from 100 to 300 A, modulated at 120 MHz with peak currents two to three times the average. The neutral gas is hydrogen or nitrogen ranging in pressure from 0.1 to 5 Torr.