Abstract:This experimental and numerical study is focused on the formation of fully ionized plasmas in ambient air by nanosecond pulsed discharges, namely the thermal spark. The first contribution of this article is the experimental charaterization of the electron number density during the pulse. The increase of the electron number density from 1016 to 101 cm-3 was measured with sub-nanosecond resolution via three techniques based on optical emission spectroscopy (OES): Stark broadening of Hα, Stark broadening of N+/O+… Show more
“…Given the high current at low voltage, the short inter-pulse period suggesting a not negligible initial charge density, and the erosion of the electrodes shown in figure A.2, makes us assume that the discharge is in the spark regime [63]. Adjacent regimes like glow or thermal spark are deemed less likely [8,46,64]. For example, NRP glow discharges occur only in narrow parameter ranges [8].…”
A novel pulsed power source capable of nanosecond pulses with burst frequencies up to 1MHz is employed to create
atmospheric pressure pulsed plasma in pure CO2 gas. The short bursts contain up to four nanosecond pulses. The CO2 conversion and corresponding energy efficiency are measured ex-situ with Fourier-transform infrared absorption spectroscopy. Trends in the absorption line profile of in-situ quantum cascade laser infrared absorption spectroscopy indicate an elevated vibrational temperature of CO2 with an increasing number of pulses per burst. The key result of this paper is that the dissociation energy efficiency is higher when operating the plasma in burst mode. Furthermore, a larger number of pulses in a burst is associated with a further increase of the dissociation efficiency. The highest efficiency measured is (17.7 ± 0.3)% for single pulses spaced 2 ms apart, and (20.0±0.3)% for bursts of three pulses, with an in-burst frequency of 1MHz and bursts spaced 4 ms apart.
“…Given the high current at low voltage, the short inter-pulse period suggesting a not negligible initial charge density, and the erosion of the electrodes shown in figure A.2, makes us assume that the discharge is in the spark regime [63]. Adjacent regimes like glow or thermal spark are deemed less likely [8,46,64]. For example, NRP glow discharges occur only in narrow parameter ranges [8].…”
A novel pulsed power source capable of nanosecond pulses with burst frequencies up to 1MHz is employed to create
atmospheric pressure pulsed plasma in pure CO2 gas. The short bursts contain up to four nanosecond pulses. The CO2 conversion and corresponding energy efficiency are measured ex-situ with Fourier-transform infrared absorption spectroscopy. Trends in the absorption line profile of in-situ quantum cascade laser infrared absorption spectroscopy indicate an elevated vibrational temperature of CO2 with an increasing number of pulses per burst. The key result of this paper is that the dissociation energy efficiency is higher when operating the plasma in burst mode. Furthermore, a larger number of pulses in a burst is associated with a further increase of the dissociation efficiency. The highest efficiency measured is (17.7 ± 0.3)% for single pulses spaced 2 ms apart, and (20.0±0.3)% for bursts of three pulses, with an in-burst frequency of 1MHz and bursts spaced 4 ms apart.
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