Abstract
The discharge characteristics and mechanism of pulse modulated radio frequency (RF) atmospheric pressure glow discharge (APGD) are studied using a two-dimensional self-consistent numerical fluid model. The ignition of an RF discharge burst is demonstrated by the increase in RF current amplitude and evolution of the discharge spatial profile from a bell shape to a double-hump shape. With a time interval of 80 µs between two consecutive RF discharge bursts, the electron dissipation after an RF discharge burst is shown, whose reduction slope changes from 1.7 × 1022 m−3s−1 to 9.1 × 1019 m−3s−1 with a time delay. The corresponding electron dissipation mechanism is proposed to be the electron loss due to reactions in the discharge bulk and the drift of electrons across the discharge gap, which explains the continuum and discrete operation modes in pulse modulated RF APGD.
Highlights
Atmospheric pressure glow discharges (APGDs) can produce a uniform and stable nonthermal plasma in an open environment without the need of vacuum equipment, which potentially can be employed in a wide application scope of surface modification,1,2 film deposition,3,4 sterilization,5 and ozone generation
Given that the power consumption and gas temperature of RF APGD are higher than those in APGD with the excitations in the kilohertz range, the pulse modulated (PM) RF APGD was proposed to separate the RF discharge into RF discharge bursts, in which the discharge characteristics can be manipulated by modulation pulses, the input energy coupling is less efficient than the continuous counterpart
The simulated RF current during the ignition phase of an RF discharge burst is found to be dependent on the time interval between the consecutive RF discharge bursts
Summary
Atmospheric pressure glow discharges (APGDs) can produce a uniform and stable nonthermal plasma in an open environment without the need of vacuum equipment, which potentially can be employed in a wide application scope of surface modification, film deposition, sterilization, and ozone generation. Compared to the discharges generated by direct current and kilohertz excitations, APGD excited by radio-frequency (RF) power has high plasma density and chemical reactivity with reduced gas breakdown voltage and discharge maintenance voltage. Given that the power consumption and gas temperature of RF APGD are higher than those in APGD with the excitations in the kilohertz range, the pulse modulated (PM) RF APGD was proposed to separate the RF discharge into RF discharge bursts, in which the discharge characteristics can be manipulated by modulation pulses, the input energy coupling is less efficient than the continuous counterpart. The discharge mechanism of an RF discharge burst was found to be dependent on the modulation pulses, which demonstrated experimentally by spatiotemporal evolution of discharge during the ignition phase that there were three operation modes, such as continuous mode, discrete mode, and transition mode. It was proposed that the ignition of an RF discharge burst was assisted by the residual electrons from the previous RF discharge burst, which reduced the ignition time an RF discharge burst takes to reach stable operation. the dynamics of residual electrons after the RF discharge burst were not clear, which plays an important role in the discharge characteristics and mechanism of PM RF APGD. Compared to the discharges generated by direct current and kilohertz excitations, APGD excited by radio-frequency (RF) power has high plasma density and chemical reactivity with reduced gas breakdown voltage and discharge maintenance voltage.. Given that the power consumption and gas temperature of RF APGD are higher than those in APGD with the excitations in the kilohertz range, the pulse modulated (PM) RF APGD was proposed to separate the RF discharge into RF discharge bursts, in which the discharge characteristics can be manipulated by modulation pulses, the input energy coupling is less efficient than the continuous counterpart.. The dynamics of residual electrons after the RF discharge burst were not clear, which plays an important role in the discharge characteristics and mechanism of PM RF APGD. A two-dimensional selfconsistent numerical fluid model was developed in helium at atmospheric pressure to study the spatiotemporal evolution and dynamics of PM RF APGD, especially to understand the residual electron dissipation mechanism between two consecutive RF discharge bursts
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