The plasma pencil: a novel cold plasma source for low temperature applications

Abstract

Summary form only given. One of the attractive characteristics of nonequilibrium plasmas is their enhanced chemistry without the need for elevated gas temperatures. This is because the chemistry is driven by the energetic electrons, while the heavy particles remain at low energy. To enhance the gas chemistry, the electron energy distribution function can be controlled in a way to shift it towards the high-energy tail. Because of these properties, non-equilibrium plasmas have recently been extensively used in various material processing applications where advanced chemical processes under low temperature conditions are desirable. One of the emerging uses of cold plasmas is in biomedical applications. In this paper we report on a novel pulsed cold source, the plasma pencil, and its unique characteristics. The pencil is capable of generating a cold plume several centimeters in length. It exhibits low power requirements and by using helium as a carrier gas the gas temperature remains low even after hours of operations. The plume emitted by the pencil can be touched by bare hands and can be directed manually by a user to come in contact with delicate objects and materials including skin and dental gum without causing any heating or painful sensation. The main characteristics of the pencil will be discussed. These include a study of its current-voltage characteristics, its emission spectra for different gas mixtures, and using fast photography we elucidate the time and spatial evolution of the plume