Analysis of the self-pulsing operating mode of a microdischarge

Abstract

The self-pulsing regime of a microhollow cathode discharge in argon is reported. The plasma is generated inside the hole drilled in an anode-dielectric-cathode device. The hole dimension ranges from 200 to 400 µm and the gas pressure ranges from 40 to 200 Torr. It is shown by optical spectroscopy and fast CCD imaging that the current pulse is related to a fast expansion of the plasma outside the microhole on the cathode backside. The pulse current duration ranges from 0.4 to 2 µs depending on the gas pressure. The self-pulsing regime occurs at medium current range (0.1-1 mA). At lower current the discharge is steady and the plasma is confined inside the hole (abnormal regime); at higher current, the plasma is steady and the plasma expands outside the hole on the cathode backside. The self-pulsing frequency is a linear function of the averaged discharge current and decreases with the device capacitance. The dependence of the self-pulsing characteristics (frequency, light emission, power deposition, etc) on the gas pressure follows a Paschen-like law; this is interpreted in considering that the fast expansion of the plasma outside the hole is similar to a gas breakdown. A simple electrical model, using a bistable voltage-controlled variable resistor to simulate the evolution of the plasma impedance, provides qualitative results in good agreement with the experiments.

Effect of limiting the cathode surface on direct current microhollow cathode discharge in helium

“…Other teams usually use much thicker cathodes ͑about 100 m͒. [8][9][10][11] As a consequence, they have observed a positive V-I slope at a low current in good agreement with the same model. The breakdown voltage values have a Paschen law behavior as also observed by other teams.…”

“…The breakdown voltage values have a Paschen law behavior as also observed by other teams. 9 After breakdown, we observed a self-pulsing regime of the microdischarge, which was studied in detail by Rousseau and Aubert. 10 During increasing current, the discharge is no longer confined inside the cavity.…”

“…These characteristics were obtained by measuring the current during linear increase and decrease in supply voltage ͑40 s period͒. Up until now, experiments carried out by other teams [8][9][10][11] with the same MHC configuration have shown the existence of an abnormal glow regime for small values of the discharge current. 12 The effect of the cathode thickness has been predicted by a model 12 based on solutions of fluid equations in the drift-diffusion approximation for the electron and ion transport coupled with Poisson's equation.…”

Electrical characterization and an equivalent circuit model of a microhollow cathode discharge reactor

“…In another study, Aubert et al 10 modeled the selfpulsing behavior of a MHCD reactor using argon as the gas at pressures from 40 to 200 Torr (5.3 to 26.6 kPa). The authors modeled the reactor as a capacitor in parallel with a resistor and a voltage-controlled switch.…”

Modes of oscillation in a high pressure microplasma discharges

“…At the right side of the Paschen curve, a smaller field distortion can trigger instability. For a micro-hollow cathode (MHC) configuration this type of instability is experimentally observed and is identified as a relaxation type of oscillation [11,12]. A two-dimensional fluid model has been employed to simulate MHC discharge and to numerically investigate the instability.…”