Plasma self-organisation in High Power Impulse Magnetron Sputtering Discharges

We report for the first time on instabilities of High Power Impulse Magnetron Sputtering Plasmas (HIPIMS) which are likely to be of the generalised drift wave type. They are characterized by well defined regions of high and low plasma emissivity along the racetrack of the magnetron and causes periodic shifts in floating potential. The azimuthal mode number m depends on plasma current, plasma density, and gas pressure. The structures rotate in vec E × vec B direction at velocities of ~10 kms^-1 and frequencies up to 200 kHz. Collisions with residual gas atoms slow the rotating wave down, whereas the elevated plasma density accelerates it. The instabilities result in intermittent modulated particle fluxes with significant magnitude transported away from the cathode.