Sub-60 °C atmospheric helium–water plasma jets: modes, electron heating and downstream reaction chemistry

Abstract

To cite this version:J J Liu, M G Kong. Sub-60°C atmospheric heliumwater plasma jets: modes, electron heating and downstream reaction chemistry. Journal of Physics D: Applied Physics, IOP Publishing, 2011, 44 (34) AbstractFor plasma treatment of many heat labile materials (e.g. living tissues) that are either moist or contain a surface layer of liquid, it is desirable that the gas plasma is generated at atmospheric pressure for process convenience and with a gas temperature ideally no more than 60 o C for mitigating permanent damage to the integrity of the test material. This implies that the liquid-containing plasma needs to be of low energy and that plasma treatment should be based largely on non-equilibrium reaction chemistry. In this contribution, a class of sub-60 o C atmospheric helium-water plasma jets is studied in terms of their main physiochemical properties. It is shown that there are five distinct modes appearing in the sequence of, with increasing voltage, the first chaotic mode, the plasma bullet mode, the second chaotic mode, the abnormal glow mode, and the nonthermal arc mode. Its chaotic modes may be sustained over a wide range of water vapour concentration (0 -2,500ppm). Compared to other liquid-containing plasmas, the He-H 2 O plasma jet operated below its nonthermal arc mode has several distinct advantages, namely very low energy consumption (2 -10 J per pulse), sub-60 o C gas temperature,

Chaos in atmospheric-pressure plasma jets

“…Effectively, these results reveal a previously unknown dimension of varying plasma chemistry. It is worth noting that with this paper, chaos has been observed in low-temperature atmospheric plasma jets in helium mixture with both oxygen [14,15] and water vapor [13]. It is conceivable that it may exist in atmospheric plasmas in other gas mixtures and indeed other electrode configurations.…”

“…A key advantage of the DBD jet configuration is that the reactive species generated in the capillary are effectively transported to a downstream sample where they are able to interact without compromising the stability of the device [11,12]. Depending on dissipated electric power, these atmospheric plasmas have been shown to operate in different modes including Townsend, glow and nonthermal arc modes, all modulated at the driving frequency [13]. Recently, however, it has been reported that atmospheric-pressure plasma jets can exhibit chaotic behavior under certain conditions [13][14][15].…”

“…Depending on dissipated electric power, these atmospheric plasmas have been shown to operate in different modes including Townsend, glow and nonthermal arc modes, all modulated at the driving frequency [13]. Recently, however, it has been reported that atmospheric-pressure plasma jets can exhibit chaotic behavior under certain conditions [13][14][15]. From the standpoint of practical applications, chaotic behaviors of atmospheric plasmas raise questions of whether their interactions with a sample may become nonlinear with respect to time, particularly when the sample contains living organisms.…”

Effective dose delivery in atmospheric pressure plasma jets for plasma medicine: a model predictive control approach

“…Thus, the plasma is susceptible to instabilities and transition to arc or spark when small changes in electrical properties occur. Distinct modes have been reported for RF-APPJs, where mode transitions can occur via the sheath breakdown events associated with secondary electron emission from the electrode surface [34][35][36]. Mode transitions can lead to high current densities and negative differential conductivity, resulting in instabilities and arc-like behavior that can inflict damage on the target substrate [37,38].…”

The transition mechanism from a symmetric single period discharge to a period-doubling discharge in atmospheric helium dielectric-barrier discharge

“…[10][11][12] Recently, more complex temporal nonlinear behaviors of APGD, such as period-doubling bifurcation and chaos, have been frequently observed in both experiments and numerical simulations. [13][14][15][16][17][18][19] Different from the single period discharge, the current pulses in period-doubling and chaos discharges repeat at multiple applied voltage cycles or fluctuate stochastically. These nonlinear behaviors are sensitive to discharge parameters and can be caused by the fluctuations of a variety of control parameters, such as the driving frequency, voltage amplitude, and gap width.…”