Amplitude Scaling of Asymmetry-Induced Transport

摘要

Our initial experiments on asymmetry-induced transport in non-neutral plasmas found the radial particle flux at small radii to be proportional to φ_a~2, where φ_a is the applied asymmetry amplitude. Other researchers, however, using the global expansion rate as a measure of the transport, have observed a φ_a~1 scaling when the rigidity (the ratio of the axial bounce frequency to the azimuthal rotation frequency) is in the range one to ten. In an effort to resolve this discrepancy, we have extended our measurements to different radii and asymmetry frequencies. Although the results to date are generally in agreement with those previously reported (φ_a~2 scaling at low asymmetry amplitudes falling off to a weaker scaling at, higher amplitudes), we have observed some cases where the low amplitude scaling is closer toφ_a~1. Both the φ_a~2 and φ_a~1 cases, however, have rigidities less than ten. Instead, we find that the φ_a~1 cases are characterized by an induced flux that is comparable in magnitude but opposite in sign to the background flux. This suggests that the mixing of applied and background asymmetries plays an important role in determining the amplitude scaling of this transport.