Efficient Radio Frequency Inductive Discharges in Near Atmospheric Pressure Using Immittance Conversion Topology

Abstract

A radio frequency (rf) inductive discharge in atmospheric pressure range requires high voltage in the initial startup phase and high power during the steady state sustainment phase. It is, therefore, necessary to inject high rf power into the plasma ensuring the maximum use of the power source, especially where the rf power is limited. In order to inject the maximum possible rf power into the plasma with a moderate rf power source of few kilowatts range, we employ the immittance conversion topology by converting a constant voltage source into a constant current source to generate efficient rf discharge by inductively coupled plasma (ICP) technique at a gas pressure with up to one atmosphere in argon. A novel T-LCL immittance circuit is designed for constant-current high-power operation, which is practically very important in the high-frequency range, to provide high effective rf power to the plasma. The immittance conversion system combines the static induction transistor (SIT)-based radio frequency (rf) high-power inverter circuit and the immittance conversion elements including the rf induction coil. The basic properties of the immittance circuit are studied by numerical analysis and verified the results by experimental measurements with the inductive plasma as a load at a relatively high rf power of about 4 kW. The performances of the immittance circuit are also evaluated and compared with that of the conventional series resonance circuit in high-pressure induction plasma generation. The experimental results reveal that the immittance conversion circuit confirms injecting higher effective rf power into the plasma as much as three times than that of the series resonance circuit under the same operating conditions and same dc supply voltage to the inverter, thereby enhancing the plasma heating efficiency to generate efficient rf inductive discharges.

Validity of Electron Temperature Measurement by Using Boltzmann Plot Method in Radio Frequency Inductive Discharge in the Atmospheric Pressure Range

“…Radio frequency inductive plasmas were generated in a device known as a RIP (RF Inverter Plasma torch) [12][13][14][15][16][17]. The plasmas were sustained in a cylindrical Pyrex glass chamber having an inner diameter of 70 mm and length of 200 mm by applying a rf power from a static induction transistor (SIT) inverter power source.…”

“…Recently, radio frequency rf-inductive plasmas in the atmospheric pressure range have been developed using a author's e-mail: ohno@ees.nagoya-u.ac.jp static induction transistor (SIT) inverter power source [12][13][14][15][16][17]. However, in order to use these rf-inductive plasmas in industrial and environmental applications, it is necessary to measure the plasma parameters (electron temperature, T e , and electron density, n e ) as a way to elucidate the quality of the generated plasmas.…”

Plasma applicators at RF and microwave frequencies

“…Thus, for capacitively coupled plasmas, the plasma efficiency decreases as the power increases and the sheath voltage increases. Therefore, it is necessary to design dynamically variable components, preferably with automated electromechanical drives for tuning vacuum variable capacitors, as well as to have special design consideration for the power inverter section [64]. Due to the reduced loss of electrons in ICPs, the plasma densities attained in these are much higher than those in CCPs.…”

Study on Effect of Inductively Coupled Ar/O₂ Plasma in E- and H-Mode on Riceberry Rice by SEM/EDS

“…H-mode was sustained by the electromagnetic field [13]. M. A. Razzak et al [14] reported that plasma in E-mode occurred ring-shaped nearly around the discharge chamber closing to the inductive electrode. However, the H-mode was in the form of the volumetric induction plasma.…”