Microhollow cathode sustained discharges: comparative studies in micro- and equivalent macro-cell geometries

We present an experimental study of discharge initiation in a three-electrode configuration consisting of a microhollow cathode discharge (MHCD) and a third planar electrode, biased positively and placed some distance away. This work is based on the microcathode sustained (MCS) configuration where the MHCD acts as a plasma cathode and enables the generation of a stable, non-equilibrium plasma at high pressure in the volume between the MHCD and the third electrode. Our experiments were carried out in two different set-ups, one using a MHCD as a cathode and another in an "equivalent" macrocell geometry, easier to implement and operating at lower pressure in which the same phenomena are observed. Consistent with previous modeling results, we find that the plasma column in the volume between the MHCD and the third electrode is characterized by a low reduced electric field, with values similar to those expected for a positive column. The ignition voltage of the plasma column depends on the voltage difference between the MHCD and the third electrode, the MHCD current, and the gas pressure and gap spacing.