A diffuse argon plume generated downstream of an atmospheric pressure plasma jet equipped with a positively biased electrode

Abstract

Compared with the diffuse mode of helium plasma jets, a filamentary mode is normally produced in the plasma plume with less expensive inert gas, such as argon, which is undesirable because intense discharge in the filamentary mode may cause damage to fragile samples. Many efforts have been attempted to realize the diffuse mode of an argon plasma jet. In this paper, the diffuse mode is realized in an atmospheric pressure argon plasma jet with increasing biased voltage (V b) applied to a downstream plate electrode. Results show that the diffuse mode transits from the filamentary mode with the increase of V b. Waveforms of voltage, current and integrated light emission reveal that the filament originates from a positive discharge with a needle anode, while the diffuse mode results from negative discharges with a needle cathode, which consist of a Trichel-pulse phase and a slower-varying phase. By fast photography, the positive discharge is attributed to a streamer regime, whereas the negative discharges belong to a Townsend-discharge regime. From optical emission spectroscopy, electron density, electron excitation temperature, vibrational temperature, and rotational temperature are studied as functions of V b.

Complicated streamer dynamics in petal‐like patterns formed on the substrate downstream of an argon plasma jet

“…Typical spectral lines include the second positive system of N 2 ($${C}^{3}{{\rm{\Pi }}}_{{\rm{u}}}\to {B}^{3}{{\rm{\Pi }}}_{{\rm{g}}}$$) and the first negative system of $${{\rm{N}}}_{2}^{+}$$ ($${B}^{2}{\sum }_{{\rm{g}}}^{+}\to {X}^{2}{\sum }_{{\rm{g}}}^{+}$$). [ 49 ] There are also spectral lines of Ar I corresponding to 4p→4 s transitions, [ 50 ] whose relative intensities increase with increasing Q . Through the collisional broadening of spectral lines (840.9 and 842.5 nm of Ar I), air content can be estimated.…”

“…+ ). [49] There are also spectral lines of Ar I corresponding to 4p→4 s transitions, [50] whose relative intensities increase with increasing Q. Through the collisional broadening of spectral lines (840.9 and 842.5 nm of Ar I), air content can be estimated.…”

Transition from a filamentary mode to a diffuse one with varying distance from needle to stream of an argon plasma jet

“…[21,22] That is, an argon plasma jet tends to operate in a filamentary mode. [23] Compared to the filamentary mode, the diffuse mode is more desirable in applications such as biomedicine and surface modification. [24] As a result, many efforts have been made to realize the diffuse mode of the argon plasma jet.…”

Discharge aspects of a snake‐like plasma plume generated by an atmospheric pressure plasma jet with variable argon flow rate

“…However, the plasma plume is constricted to a filament when argon is used. [31,32] Although the above-mentioned plumes, diffuse or filament, are continuously luminous to naked eyes, [26,33] fast photography reveals that they consist of discrete fast-moving plasma bullets. [34,35] To explain the formation of the plasma bullets, a streamer regime is proposed.…”