Time resolved optical emission spectroscopy in power modulated atmospheric pressure plasma jet

Abstract

Abstract:In this paper, the effects of the power modulation on atmospheric pressure plasma jet, operated in Ar+2%N 2 mixture, are studied. Time resolved optical emission spectroscopy is used for the investigation. From line and band intensities, the excitation, vibration and rotation temperatures are calculated. Their evolution during the modulation period exhibits a strong dependence on modulation frequency. For higher modulation frequencies, there is significant discrepancy in rotational temperatures calculated from OH spectra and from N 2 + spectra, which indicates that thermalisation time can reach milliseconds.

Batch processing of overlapping molecular spectra as a tool for spatio-temporal diagnostics of power modulated microwave plasma jet

“…Indeed, the highly excited rotational states are best observable in the P-branch, in the region (315-320) nm, where the fit reproduces the measured data as good as at the band head just below 310 nm. Straight Boltzmann plots shown in [44] further support this statement. The dissociative excitation of water molecules via its B A 1 1 state leading to overpopulation of highly excited OH rotational states, as discussed e.g.…”

“…Thus a more advanced method is used to modulate the microwaves by an amplitude envelope. There were a number of surfatron discharges recently investigated in the power modulated regime using the sine wave envelope; these include pure argon [43][44][45], and mixtures of Ar+N 2 [44], Ar+H 2 [46], argon and tetrakis(trimethylsilyloxy)silane (TTMS) [47].…”

Gas mixing enhanced by power modulations in atmospheric pressure microwave plasma jet

“…For comparison, the expected speed of the argon low in the discharge tube is also given, assuming idealized case with constant temperature of 2500 K. This value is based on the measurement of rotational temperature of the OH radical. This temperature, often expected to be identical with the temperature of the neutral gas, was found to vary with the phase, but not signiicantly [43].…”

“…In the jet plume, there are thus three interacting gas environ ments: (i) the argon plasma, outflowing from the discharge tube, with elevated gas temperature (in the order of several thousand Kelvin [43]) and humidity of 2600 ppm(V), (ii) cooling air at temperature lower than that in the discharge, flowing co-axially around the plasma jet, forming a gas shield around a part of the plume, with humidity around 5000 ppm(V), and (iii) the stationary ambient air at room temperature and humidity in the order of 10 000 ppm(V). The whole experiment was encompassed by plastic sheet to minimize any unwanted perturbations of the jet and its surroundings from outside.…”

“…From the point of view of frequency domain analysis, the simplest modulation of all is the modulation by sine wave. Some aspects of the influence of such modulation on atmospheric plasma jet were published recently [41][42][43][44] and were found suitable for various applications [9,45,46]. Among others, effective broadening of the active plasma region was observed for certain power modulation frequencies [42].…”