Minijet plasma sources for the build-up of an array of plasma generators for surface processing

An array of miniature size plasma jet generators might become an important tool for surface processing especially if the minijet plasma generator can operate at atmospheric pressures. Our efforts started with the design and construction of a d.c. miniature plasma jet generator but components' heating and unstable operation excluded this solution and imposed its change. In the present paper we report a successful development of an a.c. operated miniature type plasma jet generator. The frequency of the applied a.c. voltage was around 10 kHz, the value of the peak to peak voltages being up to 700 V for nitrogen gas at atmospheric pressure. The obtained time dependence of the discharge current and voltage drop over the discharge space, prove that the discharge was not of barrier type but an alternating d.c. type discharge with the mentioned frequency. The measured discharge current was of 55 mA, the measured power value being of the order of a few watts. It is important to mention that the gas flux is passing through a central hole of 0.5 mm diameter of the minijet generator, the obtained jet being very stable and operating hours without failure. In the case of an array of such minijets, due to radial expansion of plasma minijets after going out of hole, at a few millimeter distance, the jets will unite, building up a large area of uniform plasma, ideal for surface treatment at low plasma temperature. (authors)