Abstract
A new type of microwave plasma source is presented in which plasma at atmospheric pressure is generated inside a quartz rectangular flat box placed in a stripline supplied by a 2.45 GHz coaxial line. The plasma has a sheet shape and is designed for surface modification. Electric field and power flux distributions, tuning characteristics, and power characteristics (ratios of radiated, absorbed, and entering power) are numerically studied for three configurations: open, semi-closed, and closed. The calculations show that near-zero radiation reduction is possible only for the closed configuration, while the ratio of radiated power to entering power is always greater than 30% for the other configurations. The moving plunger is not sufficient for the ratio of reflected to incident power to fall below 20% for both the closed and open configurations. This is possible for the semi-closed configuration, but then the radiated power is the highest. The experiment shows that for the same entering power, the plasma volume is largest for the closed configuration and smallest for the open configuration, which we attribute to the difference in radiated power. The plasma generated using the closed stripline configuration has a larger volume than plasma generated using the rectangular waveguide.
Highlights
Microwave discharges in gases under atmospheric pressure are usually generated in dielectric tubes [1] or in the ambient air at the extension of a metal line [2], and the produced plasma has the shape of a column, flame, or torch [3,4,5]
A source of microwave plasma that is unusual in this respect is the microwave plasma sheet source (MPSS), which we developed and described earlier [15,16,17,18,19,20]
Due to its shape, such plasma is especially suitable for surface treatment, which have been successfully demonstrated for surface modification of polymeric materials such as polyethylene (PE) [21], polycarbonate (PC) [22], and poly(methyl methacrylate) (PMMA) [23] as well as for gradual etching of calcium carbonate crystals (CaCO3 ) [24]
Summary
Microwave discharges in gases under atmospheric pressure are usually generated in dielectric tubes [1] or in the ambient air at the extension of a metal line [2], and the produced plasma has the shape of a column, flame, or torch [3,4,5]. They are typically supplied from a coaxial line or—especially when higher powers are required—from a rectangular waveguide. Due to its shape, such plasma is especially suitable for surface treatment, which have been successfully demonstrated for surface modification of polymeric materials such as polyethylene (PE) [21], polycarbonate (PC) [22], and poly(methyl methacrylate) (PMMA) [23] as well as for gradual etching of calcium carbonate crystals (CaCO3 ) [24]
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