Excitation of helical shape argon atmospheric pressure plasma jet using RF pulse modulation

Abstract

The article reports the excitation of a helical argon atmospheric pressure plasma jet using a pulse-modulated 13.56 MHz radio frequency (RF) power source. This helical structure is observed in open ambient air, which is far different from the conventional conical shape. This helical structure originates due to the periodic pressure variation in the discharge region caused by pulse-modulated RF (2 kHz modulation frequency) and propagates downstream into the ambient air. The geometrical characteristics of the observed structure are explored using optical imaging. Moreover, the influence of various input parameters, viz., duty cycle, gas flow rate, and RF power, of the modulated pulse on the formation of a helical structure are studied. These helical structures have an implication on the plasma jet chemical features (enhancement of reactive oxygen and nitrogen species) as these are involved in an increase in air entrainment into the ionization region desired for various plasma applications.

Influence of pulse modulation frequency on helium RF atmospheric pressure plasma jet characteristics

“…More details on the experimental setup can be found elsewhere. [ 12 ] Helium gas was used as the discharge gas, and the flow rate was controlled through a mass flow controller (1.5–7.5 lpm flow range). Applying RF power at 13.56 MHz (both continuous wave (CW) and pulse‐modulated (PM) modes) using a commercial RF power generator (Cesar 1310) to the central electrode in the presence of helium gas inside the glass tube ignites the discharge, which flows out into the ambient air as a plasma jet.…”

“…More details on the experimental setup can be found elsewhere. [12] Helium gas was used as the discharge gas, and the flow rate was controlled through a mass flow controller (1.5-7.5 lpm flow range).…”

“…[1][2][3][4][5][6][7][8] To understand and optimize the fundamental properties of these types of discharges, various plasma jet devices have been developed and studied in recent years. [1,4,[9][10][11][12] Among them, the RF plasma jets have several advantages (over the low-frequency counterparts), like low breakdown voltage, high electron density, and more reactive species generation, etc. [6,[13][14][15][16] Extensive studies are reported in this direction to understand the characteristics of RF plasma jet in terms of discharge modes, dynamics of charged particles, plasma parameters etc.…”

A 2D steady state analytical model for atmospheric pressure RF plasma jet

“…Applying the RF power along with gas feed to the plasma device ignites the discharge within the discharge tube, which appears outside as a plasma jet in the ambient air. More details of the experimental setup can be found in the authors' previous publications [18,41,53].…”

“…Atmospheric pressure plasma jets (APPJs) are rapidly proving to be an essential tool both, for researchers as well as for industry due to their dispensability with expensive and complex vacuum systems [1,2] and their ability to generate blends of reactive oxygen and nitrogen species (RONS) at room temperature [3][4][5][6][7][8][9] which are highly suitable for a wide range of applications viz., biomedical, surface modifications, food processing, etc [1,[10][11][12]. Numerous plasma jets are described in the literature based on their electrode arrangement (linear field/crossfield/single electrode), power supply excitation frequency (DC/Pulsed DC/AC/RF/MW) and type of gas feed (rare/molecular/mixture) [8,[13][14][15][16][17][18][19]. Among the existing methods of plasma generation, RF-produced plasma jets are found to be fairly efficient in terms of power coupling, requiring relatively low breakdown voltages and yielding high concentrations of reactive species at very modest values of input power [20,21].…”