Low-frequency turbulent transport in magnetron plasmas

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Abstract
We report the results of an experiment to determine if low-frequency turbulence (frequencies less than the ion plasma frequency) seen in magnetron plasmas is responsible for the transport of electrons across magnetic field lines. This is done by finding the scaling of the electron confinement time τ on the mean-square electric field fluctuation 〈‖δE‖2〉. Turbulent transport models predict the scaling should be τ∝〈‖δE‖2〉−1. Data were taken at a constant pressure of 1.1 Pa of argon and for discharge current densities from 25 to 150 A/m2. Density fluctuations were recorded, and the maximum rms level was <5.2%. Measured values of τ ranged from 0.65 to 0.85 μs as the discharge current density was varied over its full range. Assuming the observed turbulent spectrum is composed of ion acoustic waves, we find that τ∝〈‖δE‖2〉−0.15, quite different from the prediction. We conclude low-frequency turbulence is not responsible for cross-field electron transport.

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