Dynamics of the m = 1 diocotron mode in the electron diffusion gauge experiment

The evolution of the m=1 diocotron mode is studied experimentally over a wide range of system parameters for a pure electron plasma confined in a Malmberg–Penning trap. The frequency of the m=1 diocotron mode is monitored and found to be higher than that predicted by Levy [Phys. Fluids 11, 920 (1968)] for an infinite-length plasma column. However, the experimental measurements of the m=1 mode frequency reported here are found to be in excellent agreement with the theoretical predictions for a finite-length plasma column. The growth and damping rates of the m=1 diocotron mode are also carefully measured and compared with theoretical predictions. Probably the strongest factor affecting the stability of the m=1 diocotron mode in a nonneutral plasma with a monotonically decreasing radial density profile is resistive-wall destabilization. The measured resistive growth rates are found to agree with theory, at least for moderate values of resistance. Even after minimizing the resistive-wall instability, and main...

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