Characterization of a novel microwave plasma sheet source operated at atmospheric pressure

Abstract

Typically, microwave plasma sources (MPSs) operated at atmospheric pressure deliver plasmas in the common form of flames or cylindrical columns. In contrast to that, in this paper, a novel MPS (recently patented by us) for generating a new type of plasma in the form of a plasma sheet, which is sustained within a dielectric flat cuboid box, is presented. It is waveguide based, operated at a frequency of 2.45 GHz and in argon at atmospheric pressure. The plasma sheet consists of many filaments, typical of a microwave argon plasma. The MPS is described and analyzed in terms of optical emission spectroscopy, simulation of the electric field distributions in the MPS and numerical modeling of the working gas flow. Depending on the argon flow rate and absorbed microwave power, the determined electron density and rotational temperatures of OH radicals ranged from 3.6 × 1014 to 5.6 × 1014 cm−3 and from 800–1250 K, respectively. Numerical simulations have confirmed that the dimensions of the box are chosen correctly to ensure a sufficiently homogeneous distribution of the gas flow velocity field. The calculated electromagnetic field distributions in the MPS with plasma have shown that the device is well matched to the feeding line. The relative simplicity of the presented plasma source and industrially convenient plasma shape make it attractive for practical applications in the surface treatment of various materials.