An atmospheric-pressure, room-temperature, cold micro plasma

Summary form only given. Non-equilibrium low-temperature plasmas sustained at atmospheric pressure, which are very promising for a range of advanced applications from health care and medicine to materials science and nanotechnology^1-8. Upon reduction to micrometer dimensions, plasmas not only show unique physical properties (e.g., extreme thermal non-equilibrium), but also enable an unprecedented access to a largely unexplored region of the plasma phase parameter space. Present-day micro-plasmas are confined to micro-cavities of the typical dimensions in the ten-to-hundreds micrometers and the aspect (length-to-depth/width) ratios in the 1:1 to 20:1 ranges. The electron/ion density of such micro-plasmas is typically ~10¹¹-10¹⁵ cm^-3.As the discharge size is reduced, it becomes more difficult to generate the plasma and maintain its charge neutrality (ne = ni), where ne and ni are the electron and ion densities, respectively. In this paper9, an atmospheric pressure nonequilibrium Ar micro-plasma generated inside a micro-tube with plasma radius of 3 μm and length of 2.7 cm is reported. The electron density of the plasma plume estimated from the broadening of the Ar emission line reaches as high as 3x10¹⁶cm^-3. The electron temperature obtained from CR model is 1.5 ev while the gas temperature of the plasma estimated from the N₂ rotational spectrum is close to room temperature. The sheath thickness of the plasma could be close to the radius of the plasma. The ignition voltages of the plasma increase one order when the radius of the dielectric tube is decreased from 1 mm to 3 μm.