Characterization of a DC-driven microplasma between a capillary tube and water surface

¹ Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University - Shanghai 200240, PRC
² Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering P.O. Box 218, Lindfield, NSW 2070, Australia
³ Plasma Nanoscience @ Complex Systems, School of Physics, The University of Sydney Sydney, NSW 2006, Australia
⁴ Jozef Stefan Institute - Jamova cesta 39, SI 1000 Ljubljana, Slovenia, EU
⁵ Nanotechnology & Integrated Bio-Engineering Centre (NIBEC), University of Ulster Newtownabbey, BT37 0QB, UK, EU

^(a) xxzhong@sjtu.edu.cn

Received: 5 December 2012
Accepted: 13 March 2013

Abstract

A microplasma generated between a stainless-steel capillary and water surface in ambient air with flowing argon as working gas appears as a bright spot at the tube orifice and expands to form a larger footprint on the water surface, and the dimensions of the bell-shaped microplasma are all below 1 mm. The electron density of the microplasma is estimated to be ranging from cm⁻³ to cm⁻³ for the different operating conditions, which is desirable for generating abundant amounts of reactive species. A computational technique is adopted to fit the experimental emission from the N₂ second positive system with simulation results. It is concluded that the vibrational temperature (more than 2000 K) is more than twice the gas temperature (more than 800 K), which indicates the non-equilibrium state of the microplasma. Both temperatures showed dependence on the discharge parameters (i.e., gas flow and discharge current). Such a plasma device could be arranged in arrays for applications utilizing plasma-induced liquid chemistry.