The plasma parameters of an RF-driven plasma microjet in different applied RF powers, different positions from the outlet nozzle, and various argon flow rates are investigated. A double Langmuir probe is designed and constructed, then, the electron temperature, ion density, and saturation currents along the microjet axis at different positions such as top, mid, end and out of the microjet are measured. To avoid the collision, sparking, and corrosion effects, in high pressure plasmas, on the characteristic curve, the double Langmuir probe was reciprocated linearly perpendicular to the plasma jet with a frequency of 20 Hz. The four frequently used methods of the direct fitting of the theoretically obtained formula, double slope, turning point or Dote, and cutting or intercept method are explained and used to determine the electron excitation temperature from the experimental data and shown that they lead to similar results, so, the averaged value of these results used in the evaluations of plasma densities. The plasma number density and electron temperature were measured using DLP in the jet at different axial locations. The results for the electron excitation temperature from the DLP is compared with that of obtained from the emission spectrum of the plasma jet. It has been shown that the averaged electron excitation temperature obtained using optical emission spectroscopy (1.58eV) is within the 25% of that measured by the double Langmuir probe which is same as the early reported value by other researches. Manuscript profile

An atmospheric pressure plasma microjet device with a tapered ground electrode and dielectric barrier is developed. The effects of the powered electrode geometry and input power on the specifications of the launched RF plasma jets are investigated. Needle-powered electrodes with different types, shapes, lengths, and diameters, such as perforated and un-perforated hollow cylindrical tubes with different inner and outer diameters or solid with flat tip and with sharp tip steel nail rods are examined. The effects of the discharge gap size on the launched jet lengths and widths are studied. The axial and radial components of the electric field are simulated at the device output nozzle by applying radiofrequency power to the needle electrode and their possible effects on the plasma plume generation are discussed. The variations of the launched microjet lengths and widths are investigated versus the working gas (argon) flow rates in two experiments with two different fixed input powers. It has been shown that there is an optimum flow rate to obtain maximum jet length with a suitable narrow width. The effects of nozzle diameter, how to inject gas into the system, and argon flow rates on the plasma plume characteristics are discussed through the Reynolds number. Manuscript profile

AbstractWith the argument that two-electrode DBD-like systems are much more operational than single-electrode systems in biomedical applications, targets sensitive to temperature and electric shock, the effects of parameters associated with the geometry of the grounded electrode such as its shape, size, and position it at the output of the atmospheric pressure RF plasma jet in two-electrode systems is investigated. By varying the position of the typical narrow ring grounded electrode on the dielectric tube toward the powered electrode, the ratio of the axial to radial electric field components depend on the externally applied potential to the plasma has been investigated and shown that the axial component of the electric field is maximized at certain position(s) of the grounded electrode. The analysis of the data indicates that there is an inverse relationship between the magnitude of the axial electric field in the plasma channel and the discharge ignition voltage, and a direct relationship with the plasma jet length. It is known that by increasing the width of the ground electrode until the full covering of dielectric, the jet length increases from the dielectric output to the neighborhood near the needle electrode, and reduces the discharge ignition threshold and consequently power consumption of the jet, but increasing its width to greater than the above values does not have a significant effect on jet output. It has also been shown that by tapering the dielectric end and fully covering it with its conical-shaped electrode, the output jet length increases and decreases its width. Manuscript profile