Abstract
The two-dimensional spatially extended atmospheric plasma arrays by many parallel radio-frequency glow discharge plasma jets packed densely, represent a feature option of large-scale low-temperature atmospheric plasma technologies with distinct capability of directed delivery of reactive species and good insusceptibility to sample variations. However, it is still a challenge to form plasma jet with large area of uniform active species on a downstream substrate due to the complex interactions between individual jets. This paper proposes to numerically study the strategy and mechanism of control/modulation for the array discharge to produce two-dimensional plasma uniformity in the downstream working area. In this work, a two dimensional fluid model is employed to investigate the characteristics in the jet region of helium radio-frequency atmospheric-pressure glow discharge (RF APGD) with array generators. The influences of upstream discharge characteristics, gas flow and their cooperative effects on the distribution of species densities, gas temperatures and the uniformity of active species in the material treating area is studied, and the essential strategy for the modulation method is acquired. The results will be significant for deep understanding of coupling behaviors of multiple plasma plumes in the RF APGD array and applications of the technology.
Highlights
Radio frequency atmospheric pressure glow discharge (RF APGD) plasma sources produced by water-cooled bare-metallic electrodes possess the features of low gas temperatures, high concentrations of chemically reactive species and convenient operations in the open air, they are widely used in many application fields, such as surface modification of material, microbial breeding and plasma medicine.[1,2,3,4,5]
Plasma generators with discharge current density of Id = 16 mA/cm[2] and gas flow mean velocity v = 5 m/s in uniform distribution is employed as Case I, which is used to compare with the other cases
Characteristics in the jet region of helium radio-frequency atmospheric-pressure glow discharge with array generators are investigated by a two dimensional fluid model
Summary
Temperature fluctuation on the downstream substrate due to jet-to-jet coupling effects.[12,13,14] In this aspect, experimental studies on jet-to-jet interaction with different gas flow rates are investigated by Kim and his co-workers,[15] which reveals the effect of interactions between different plasma jets. We can use the time averaged value which considered transient effects in the discharge region as the boundary condition of the 2-D fluid model, and in the jet region we focus on the steady state distribution of active species which is critical for material treatment. The influences of gas flow and discharge characteristic on acquiring better species uniformity in the processing region with enough number densities of active species and appropriate temperature for heat-sensitive materials is discussed. (e.g., the living bio-materials and the precision instruments)
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