  The reverse discharge (RD) phenomenon in bipolar HiPIMS has been observed
when a sufficiently long positive pulse is applied to the magnetron. Due to the
magnetic field, electrons accumulated behind the magnetic trap are prevented
from reaching the positive target. Consequently, a space charge double layer
(DL) is formed between the positive target and the plasma behind the magnetic
trap, leading to electron acceleration across the DL and RD ignition. This
study reveals the significant impact of the magnetic field configuration on RD
ignition. Experiments are performed using a Ti target involving magnetic field
variation, wire probe measurements of floating potential, and optical emission
spectroscopy imaging. It is found that adjusting the magnetic field to a more
balanced configuration leads to earlier RD ignition, while a more unbalanced
one delays or even prevents it. Specifically, the time of RD ignition decreases
with an increase in the magnetic null point distance from the target. Moreover,
the size and shape of optical emission in the RD varies with nearby probe
placement, suggesting sensitivity to external electrodes.
