Alpha and gamma RF capacitance discharges in N₂at intermediate pressures

Abstract

Measurements have been made on the current and voltage characteristics and the time-resolved and time-averaged visible emission of alpha-( alpha -) and gamma- ( gamma -) type RF capacitative discharges in N2 at frequencies between 10 and 60 MHz over the pressure range 10 to 100 Torr. A time-dependent model is proposed for alpha -type discharges that yields electron energy and density, internal potentials, discharge current and power dissipation given the measured parameters of inter-electrode voltage and separation, gas pressure and RF frequency. The model predicts considerable energy dissipation in the near electrode sheaths and elucidates the increasing stability of alpha discharges for higher input powers as the RF frequency is raised.

Mode Characteristics of radio-frequency atmospheric glow discharges

“…In the mode, the gap voltage increases monotonically with the discharge current density and the differential conductivity of the discharge is positive. This trend is identical to that of available RF APGD experiment data [1]- [9], [16] and also consistent with the mode in low-pressure glow discharges [17], [18]. As the current density increases above 28 , the gap voltage increases less for a given increment in the discharge current.…”

Three modes in a radio frequency atmospheric pressure glow discharge

“…Such hysteresis has not been reported before for rf APGD although it is known for glow discharges at moderate pressures ͑10-200 Torr͒. 22 Subsequently from point G onwards the plasma recovery from the second sheath breakdown follows roughly its recovery route from the first breakdown. Therefore the rf APGD evolves from the abnormal glow mode, through the recovery mode, then back to the abnormal glow mode.…”

Radial structure of low pressure rf capacitive discharges

“…As is known [4,9,[25][26][27][28][29][30][31][32][33][34][35], a rf capacitive discharge may burn in two different modes: a weak-current (a-) and strong-current (gmode). In the a-mode the electrons acquire their energy for ionizing gas atoms in the rf field in the quasi-neutral plasma, the electron emission from the surface of the electrodes not playing a substantial role in the discharge sustainment.…”

“…In so doing we use the values of the electron temperature determined from the probe CVCs (employing the linear section of the graph of the electron current to the probe constructed to the semi-logarithmic scale). [4,9,[25][26][27][28][29][30][31][32][33][34][35] of the rf discharge (the curve for U rf ¼ 50 V, p ¼ 0.1 Torr and the curves for U rf ¼ 100 and 165 V, p ¼ 1 Torr) counting from the discharge axis, the electron temperature first remains constant or increases weakly. However on approaching the wall of the discharge tube the electron temperature T e increases abruptly, its maximum value exceeding T e near the discharge axis almost more than twice.…”