Experimental observations of longitudinal space-charge waves in intense electron beams

Studies of the dynamics of longitudinal space-charge waves in space-charge dominated beams propagating through a transport channel with a long solenoid are performed at the University of Maryland. In this paper, we report some experimental results on the energy modulations converted from density modulations. By changing the working conditions of the electron gun, pure initial density modulations are generated. Energy perturbation waveforms are measured with a high-resolution energy analyzer. The experimental results are compared with both the linear theory and the simulation results. Good agreements are achieved for the relationship between the energy and current perturbation strengths.

Figure 1

Schematic of the long solenoid experiment system setup.

Figure 2

Four groups of initial currents with perturbation.

Figure 3

Mean energy waveforms derived from energy analyzer signals for different groups.

Figure 4

Current profile imported into WARP in group 3.

Figure 5

Comparisons of the profiles of the mean energy for the experiment results, WARP simulation results and one-dimensional cold fluid theory.

Figure 6

The results of mean energy vs time for different beam radius in WARP.

Figure 7

The relationship between the strength of the energy perturbation and the initial strength of the current perturbation.