  A feedforward scheme is applied for drift waves control in a magnetized
magnetron sputtering plasma. A system of driven electrodes collecting electron
current in a limited region of the explored plasma is used to interact with
unstable drift waves. Drift waves actually appear as electrostatic modes
characterized by discrete wavelengths of the order of few centimeters and
frequencies of about 100 kHz. The effect of external quasi-periodic, both in
time and space, travelling perturbations is studied. Particular emphasis is
given to the role played by the phase relation between the natural and the
imposed fluctuations. It is observed that it is possible by means of localized
electrodes, collecting currents which are negligible with respect to those
flowing in the plasma, to transfer energy to one single mode and to reduce that
associated to the others. Due to the weakness of the external action, only
partial control has been achieved.
