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Electron transport and mobility is studied in the presheath and the extended presheath (also called the bulk plasma) of a high power impulse magnetron sputtering (HIPIMS) plasma. The azimuthal currents above the racetrack has significant contributions from three sources, (1) the pressure gradient, (2) the combined gradB and curved vacuum field drift, and (3) the electron Hall (E/B) drift. The resulting cross-B electron drift speed is high above the thresholds for the modified two-stream instability, and also the lower hybrid drift instability. A scaling comparison is made to a basic plasma experiment on plasma penetration across a magnetic barrier (Hurtig T., Brenning, N., and Raadu, M. A., Phys Plasmas 12, 012308, 2005), where anomalous electron cross-B mobility was quantitatively related to a corresponding electron cross-B drift speed, and where parameters are close to those in the HIPIMS magnetron. It is found that a close analogy can be made, based on normalization of parameters, which indicates that the same class of anomalous resistivity is operating in the two devices. In the HIPIMS magnetron this results in azimuthal oscillations in the electric field, in the range of the lower hybrid frequency flh = (fgifge)1/2, about 2-3 MHz. The wave structure in the instability give an azimuthal momentum exchange between ions and electrons that corresponds to an effective e-i collision frequency (ωgeτc)eff = 2 , i.e., far exceeding the value from Bohm diffusion, (ωgeτc)eff = 16. The results help to explain previously seen experimental results and further develop an understanding for HIPIMS and DC magnetron sputtering. |