Spatio-temporal distribution of absolute densities of argon metastable 1s5 state in the diffuse area of an atmospheric pressure nanosecond pulsed argon microplasma jet propagating into ambient air

Abstract

Atmospheric microplasma jets (MPJs) sustained in rare gases have gained increased attention due to their potential to generate highly reactive species. In this paper, we present space- and time-resolved argon metastable densities, Ar(1s5), measured in an atmospheric pressure MPJ operated in Ar and propagating into ambient air using tunable diode laser absorption spectroscopy (1s5 → 2p9 optical transition). The MPJ was produced using a dielectric barrier discharge energized by short duration (230 ns) high-voltage positive pulses (4.2–6.2 kV) at a repetition frequency of 20 kHz. The spectral absorption line profile was recorded and allowed measurements of the absolute metastable Ar(1s5) density integrated in the line-of-sight of the laser beam under various operating conditions of the MPJ. The results reveal a sensitive dependence of the Ar(1s5) density on spatial coordinates, i.e., distance from the exit of the capillary tube of the discharge and from the axis of the argon jet. The highest Ar(1s5) densities of about 3 × 1013 cm−3 were measured at the axis of the argon jet at longitudinal distances between 4 and 5.5 mm downstream from the nozzle of the tube. The temporal distribution of the Ar(1s5) density, which presents three maxima, is thoroughly discussed in this paper. The spatial distribution of the effective Ar(1s5) lifetime (<250 ns) is also reported, giving some insight into the surrounding environment of the argon metastable atoms. The determined spatiotemporal distributions of the Ar(1s5) density can be useful for the optimization of argon MPJs for different applications like surface or biomedical processes.

Experimental investigation of a ns-pulsed argon plasma jet for the fast desorption of weakly volatile organic compounds deposited on glass substrates at variable electric potential

“…A higher density of Ar metastables should lead to a higher desorption efficiency, since a higher number of metastables impact the Bibenzyl deposits. The Ar(1s5) metastable density measured in the present work is higher than that of the free (no target) Ar APPJ [40]. To the best of our knowledge, only one work studied the effect of a target on the Ar(1s5) densities in Ar APPJs [28].…”

A KHz frequency cold atmospheric pressure argon plasma jet for the emission of O(1S) auroral lines in ambient air

“…The argon emission that results in the metastable state clearly shows us that this state is highly populated. Studies of the argon metastable density in atmospheric plasma jets yield a density of 26 – 28 . Once the atomic oxygen is created, the O( S) state is formed through a variety of reaction pathways.…”

Periodic forced flow in a nanosecond pulsed cold atmospheric pressure argon plasma jet

“…The temporal evolution of the HV pulse is shown in Figure 2(b.). For all the conditions shown in the present paper, the applied voltage amplitude is fixed at 6 kV, for which the discharge peak current is of about 175 mA and the energy deposited per pulse is of about 20 µJ [11], [13], [16], [20]. For each burst event, the delay of the first HV pulse, the number of HV pulses and the PRF can be controlled.…”

“…Also, it is worth mentioning that among the wide variety of CAPPJ devices found in the literature, independently of the buffer gas used, the gas injection geometry, resulting from the HV electrode assembly, widely differs. Depending on the gas injection geometry used, the gas can flow, prior to its expansion outside of the capillary, through a hollowed inner HV electrode inserted inside the capillary [12], [13], [17], [16], [19], [20], [28], [44], [45], [53], [60], [61] or around a needle HV electrode [26], [29], [38], [43], [46], [47]. External HV ring electrodes wrapped around the capillary are also used [25], [27], [49], [32]- [34] and, in this case, do not interfere with the gas flow.…”