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A CH3F:O2 (50%:50%) inductively coupled discharge, sustained in a compact plasma reactor, was investigated as a function of power (20-400 W) and pressure (9-30 mTorr), using optical emission spectroscopy and Langmuir probe measurements. The electron density increased linearly with power but only weakly with pressure. The effective electron temperature was nearly independent of power and pressure. The gas temperature, obtained from the rotational structure of N2 (C → B) optical emission, increased from 400 to 900 K as a function of inductive mode power between 75 and 400 W at 10 mTorr. For constant feed gas flow, the absolute H, F, and O atom densities, estimated by optical emission rare gas actinometry, increased linearly with power. The absolute number density ratios H/Ar, F/Ar, and O/Ar, increased, decreased, and remained constant, respectively, with pressure. The H-atom density was estimated to be 5.4 × 1013 cm-3 at 400 W and 10 mTorr (gas temperature = 900 K), implying a high degree of dissociation of the CH3F feedstock gas. The F and O atom number densities were much lower (8.3 × 1012 cm-3 and 5.9 × 1012 cm-3, respectively) for the same conditions, suggesting that most of the fluorine and oxygen is contained in reaction products HF, CO, CO2, H2O, and OH. The relative number densities of HF, CO, and CO2 were observed to first rapidly increase with power, and then reach a plateau or decay slightly at higher power. Reaction mechanisms were proposed to explain the observed behavior of the number density of F and HF vs. power and pressure. [ABSTRACT FROM AUTHOR]

Plasma bullets generated by atmospheric pressure low temperature plasma jets have recently been an active research topic due to their unique properties and their enhanced plasma chemistry. In this paper, experimental insights into the plasma bullet lifetime and its velocity are reported. Data obtained from intensified charge-coupled device camera and time-resolved optical emission spectroscopy (OES) elucidated the existence of a weakly ionized channel between the plasma bullet and its source (such as the plasma pencil). Factors responsible for the inhibition of the propagation of the bullet, such as low helium mole fraction, the magnitude of the applied voltage, and the secondary discharge ignition time, are also revealed. A new technique is discussed to accurately measure the plasma bullet velocity, using time-resolved OES. This new technique shows that during its lifetime the plasma bullet goes through launching, propagation, and ending phases. In addition, it is noted that the plasma bullet exhibits an unstable behavior at the early beginning and late ending of the propagation. [ABSTRACT FROM AUTHOR]

Using an electrical discharge to control airflow has recently been an active area of research. This is mostly because of the interest in the manipulation of free airflow for aerodynamic applications. Corona discharges are well suited for these applications. In this paper, we present photographs illustrating the ion wind effect in a clear visual manner. The device used is a positive corona discharge between the end of sharp wires and a grounded mesh electrode. Measurements of the average wind speed as a function of the applied voltage for two different gap distances are presented. Index Terms--Actuators, aerodynamic, airflow, corona, electrical discharge, ion wind.

CH3F/O2 inductively coupled plasmas at 10 mTorr were investigated using optical emission spectroscopy. A ‘self-actinometry’ method was developed to measure the absolute number density of CO that formed in reactions following dissociation of CH3F and O2 in the plasma. In this method, small amounts of CO were added to the plasma, leading to small increases in the CO emission intensity. By carefully accounting for small perturbations to the plasma electron density and/or electron energy distribution, and by showing that very little of the CO added to the plasma was decomposed by electron impact or other reactions, it was possible to derive absolute number densities for the CO content of the plasma. With equal fractions (0.50) of CH3F and O2 in the feed gas, the CO mole fraction as a function of plasma power saturated at a value of 0.20–0.25. As O2 in the feed gas was varied at a constant power of 100 W, the CO mole fraction went through a maximum of about 0.25 near an O2 feed gas fraction of 0.5. The relative CO number densities determined by ‘standard’ actinometry followed the same functional dependence as the absolute mole fractions determined by self-actinometry, aided by the fact that electron temperature did not change appreciably with power or feed gas composition. [ABSTRACT FROM AUTHOR]

Measured relative densities as a function of O2 addition in a CH3F/O2 inductively coupled plasma changed abruptly for H, O, and particularly F atoms (factor of 4) at 48% O2. A corresponding transition was observed in electron density, effective electron temperature, and gas temperature, as well as in C, CF, and CH optical emission. These abrupt transitions were attributed to the reactor wall reactivity, changing from a polymer-coated surface to a polymer-free surface and vice-versa, as the O2 content in the feed gas crossed 48%. [ABSTRACT FROM AUTHOR]