The plasma properties in a magnetron sputtering source can be modified by inducing the hollow cathode effect in a groove machined into the cathode target. Neutral gas is fed directly into the groove supplied from a reservoir behind the target and this is found to significantly increase the discharge current. Langmuir probe measurements made above the sputter trench show a much denser plasma is formed and the proportion of hot electrons in the plasma bulk is increased when gas is fed to the groove rather than to the vacuum chamber. The new design allows low downstream working pressures to be achieved but still maintaining high discharge currents, and gives the ability to run the discharge in one gas while introducing a second (i.e., reactive gas) to the chamber close to the substrate.