DC glow microdischarge with a self-determined length in helium and argon at atmospheric pressure

The spatial characteristics of a stable DC glow microdischarge with currents of 1-20 mA ignited between a flat cathode and truncated cylindrical anode with a diameter of 100 μm in helium and argon at atmospheric pressure were studied. The focus of the present study is on the examination of the experimental conditions to obtain a stable and homogeneous state of the microdischarge at an electrode gap of 15-1500 μm. It is shown that such conditions are fulfilled when the parameter pL₀ (p - gas pressure at 300 K; L₀ - electrode gap) corresponds to the values near the minimum of the Paschen curve, and the microdischarge choses its length, that is the microdischarge has a self-determined length. The main measured parameters are the voltage drops across the electrode gap and the discharge currents. In addition, the size and shape of the negative glow region of the discharge, cathode current density, and other characteristics were estimated.