Leo Mendel D. Rosario

Characterization of a Microwave-Induced Atmospheric-Pressure Ar–N 2 Plasma Pencil

A microwave-induced atmospheric-pressure plasma pencil was developed with an Ar–N2 gas mixture supplied to a coaxial transmission line. High-frequency simulation showed sufficient high electric field at the tip of the inner conductor, which resulted to automatic plasma ignition and a stable operation. The dependence of the characteristics of the plasma pencil from Ar and N2 gas flow rates was extensively studied. At moderate Ar gas flow rates, the plasma pencil can be operated at several tens of watts to achieve a near room-temperature and centimeter-long Ar–N2 plasma plume with OH and NO radicals as active species. Optical emission spectroscopy was also used to determine the vibrational and rotational temperatures of the plasma pencil. The vibrational temperature of N2 from the second positive system (2PS) can be obtained at moderate gas flow rates, since there was a good linear fitting with the Boltzmann distribution. At these gas flow rates, the vibrational and rotational temperatures of N2 from 2PS were found to be 0.42 and 0.29 eV, respectively.

A 2.45-GHz Microwave Air Plasma Under a Double-Hexapole Magnetic Field

Presented here is an image of a microwave air plasma produced from a 2.45-GHz source. To assist in the plasma ignition and confinement, a set of samarium-cobalt (Sm-Co) permanent magnets arranged in a double-hexapole configuration is used. In the image presented, air in the vacuum chamber is ignited into the plasma at a pressure of 3 × 10-3 torr. The plasma exhibits a distinct pattern where brighter areas appear at alternate regions of magnetic cusps. Based on particle-in-cell simulations, the bright areas coincide with regions where the electron energies and electron densities are relatively high.

High Dynamic Range Imaging of Magnetized Sheet Plasma

High dynamic range (HDR) imaging was used to obtain a wide intensity map of a magnetized sheet plasma. A set of 12 low dynamic range (LDR) photographs with various shutter speeds (1/200-1/2 s) was captured with an Olympus FE-19 digital camera. The LDR images were processed to recover color channel response functions of the camera needed to produce RGB radiance maps. The HDR image was finally generated from the combined radiance maps via linear tone mapping. By comparison of histograms, the HDR image uses the whole range of intensity values compared with the underexposed and overexposed LDR images.