Evolution of the resistive hose instability in full density air

The resistive hose instability of an intense electron beam (1 MeV, 2–10 kA)is experimentally investigated in full density air (630 Torr - Albuquerque, NM) by varying beam current, emittance, and initial transverse motion. Hose frequency, amplitude, and growth rates are plotted against distance, time, and current. The spatial and temporal evolution of these quantities is used to follow hose behavior from the linear to the nonlinear regime. The first betatron wavelength appears to be especially important to hose behavior in the linear regime and, in the nonlinear regime, the instability has been found to move to higher frequencies.