  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.
