Cathode current distributions in an unbalanced magnetron

The arrival of ions and the emission of electrons from a target can be measured as a current, and it is the variation of this current with position that is the focus of this paper. To measure how the current varies a number of probes were constructed to suit a circular unbalanced magnetron. The target was sputtered in DC mode at over a range of pressures and discharge currents, in both argon and argon/oxygen atmospheres. Results indicate that the width of a Gaussian distribution function, fitted to the data, increases with discharge current, and also that pressure has a negligible effect on the shape of the distribution. The introduction of oxygen appeared to have no discernable effect, within experimental error, on the current distribution over the range of parameters tested.