Drifting Ionization Zone in Sputtering Magnetron Discharges at Very Low   Currents
  Discharges with crossed electric and magnetic fields are known to develop instabilities that are crucial in the transport of charged particles. Sputtering magnetrons are no exception. While most recent studies focused on traveling ionization zones in high power impulse magnetron sputtering, we show here fast camera images of magnetron discharges at very low current. A single drifting ionization zone is always present, even down to the threshold current of about 10 mA. 
Andr\'e Anders, Pavel Ni, and Joakim Andersson
physics.plasm-ph