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Empirical data on streamer formation and propagation in near-atmospheric pressure N 2 and N 2 /O 2 mixtures are presented. The data were obtained primarily from high-speed, high-sensitivity shutter and streak photography of streamers produced in a ≈13 cm gap. The streamer propagation velocity as a function of applied voltage, polarity, total pressure, and O 2 concentration are provided. In addition, information on streamer bifurcation, and streamer shape and size is included. The breakdown process has two phases: a fast phase featuring the propagation of streamers, and much slower phase involving the heating of the gas to form the spark channel. Also we found that the addition of O 2 significantly alters the streamer characteristics and behavior, indicating that photoionization processes play an important role.

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This paper presents a nitrogen microplasma jet that operates at atmospheric pressure and provides details of an observation of the striated multilayer discharge patterns formed in the plasma jet. The plasma jet device in a microhollow electrode is a pencil-type configuration that produces a long cold plasma jet capable of reaching 3.5cm and having various excited plasma species shown through optical emission spectrum. By introducing a gas flow rate of more than 5l∕min, striated discharge patterns in the plasma jet are produced through ionization wave propagation.

An apparatus for generating flames and more particularly the microwave plasma burner for generating high-temperature large-volume plasma flame was presented. The plasma burner is operated by injecting liquid hydrocarbon fuels into a microwave plasma torch in air discharge and by mixing the resultant gaseous hydrogen and carbon compounds with air or oxygen gas. The microwave plasma torch can instantaneously vaporize and decompose the hydrogen and carbon containing fuels. It was observed that the flame volume of the burner was more than 50 times that of the torch plasma. While the temperature of the torch plasma flame was only 550 K at a measurement point, that of the plasma-burner flame with the addition of 0.025 lpm ͑liters per minute͒ kerosene and 20 lpm oxygen drastically increased to about 1850 K. A preliminary experiment was carried out, measuring the temperature profiles of flames along the radial and axial directions.