Rigid Rotation and Surface Envelopes of Nonneutral-Plasma Columns

The bulk rotation velocity and surface envelope of a drifting unneutralized electron beam have been measured. These measurements verify various properties predicted by nonneutral-plasma theory. One unusual feature is that in some instances, the bulk rotation is opposite to that normally associated with the equilibria. Rotation at angular velocities greater than ωc is also observed. In addition, the wavelength of the time-independent surface envelope is found to depend on the amount of ripple present.