  A cathodic arc source with a magnetron-type magnetic field was investigated
for stability, erosion, and compatibility with a linear macroparticle filter.
Here we report about unusual arc spot erosion patterns, which were narrow (~ 2
mm) with periodic pits when operating in argon, and broad (~ 10 mm) with
periodic groves and ridges when operating in an argon and oxygen mixtures.
These observations can be correlated with the ignition probability for type 2
and type 1 arc spots, respectively.
