EXPERIMENTAL TESTING BENCH FOR THE DIAGNOSTICS OF PLASMA GENERATED BY PULSED GUNS WITH THE DIELECTRIC SURFACE BREAKDOWN

The experimental testing bench “ETB-PG” was designed to study the operation of plasma guns. The constructional design of plasma guns with replaceable dielectric operating on the surface sparkover basis has been proposed. Discharge currents and voltages under atmospheric and vacuum conditions have been determined. The two types of discharges were detected in the pressure range varying from the atmospheric value to 10-5 Torr. An experimental Paschen curve has been plotted. A statistical dependence of the types of discharges on the number of pulses, the pressure in the chamber, and the breakdown voltage has been established. The results of optical studies of the plasma flow generated by plasma guns in the vacuum of 2∙10-4 to 2∙10-5 Torr have been presented. The propagation velocity of the plasma flow in axial and radial directions has been measured. The glow time of the injected plasma was determined for different types of the discharges. The spectrograms of the composition and degree of the plasma ionization have been obtained.

The Effect of Axial Magnetic Field on The Breakdown Voltage of Air at Low Pressure

To add more details about the effect of the axial magnetic field on the plasma profile, the breakdown voltage of air was investigated at low pressure (9-15 Pa) in the presence of axial magnetic field (0.01-0.04T). The air was ignited by a DC voltage between two plain electrodes of aluminum separated by a distance (8.5cm). The measurements showed that the discharge voltage decreases to a minimum value, then returns to increase over the minimum with increasing the magnetic field strength, at all pressures in the range. It was also observed that a maximum decrease in the discharge voltage is obtained near the minimum of Paschen curve from the right side. The decrease in the discharge voltage was caused mainly by the effect of magnetic flux density on the diffusion of charged particles to the walls, especially on that of free electrons which were borne during the breakdown process.

Electrical glow discharges and plasma parameter of planar sputtering system for silver target

DC planar sputtering system is characterized by varying discharge potential of (250-2000 volt) and Argon gas pressures of (3.5×10-2 – 1.5) mbar. The breakdown voltage for silver electrode was studied with a uniform electric field at different discharge distances, as well as plasma parameters. The breakdown voltage is a product of the Argon gas pressure inside the chamber and gab distance between the electrodes, represent as Paschen curve. The Current-voltage characteristics curves indicate that the electrical discharge plasma is working in the abnormal glow region. Plasma parameters were found from the current-voltage characteristics of a single probe positioned at the inter-cathode space. Typical values of the electron temperature and the electron density are in the range of (2.93 –5.3) eV and (10-16 -10-17) m-3 respectively.