Ozone generation in an atmospheric pressure micro-plasma jet in air

Summary form only given. Microhollow cathode discharges (MHCDs) offer the possibility to generate non-thermal plasmas in atmospheric pressure gases, including air, by relatively simple means. The MHCD plasma results from a direct current discharge between two molybdenum electrodes (0.25 mm thick) that are separated by an alumina insulator of the same thickness. A tapered discharge channel is drilled through all layers, leaving a 0.2 mm wide opening in the cathode and an opening of /spl sim/0.1 mm in diameter in the anode. By flowing air at atmospheric pressure through this hole, a plasma jet with typical dimensions of millimeters in the axial direction is generated. The gas temperature of the jet can be controlled by varying the gas flow rate. At high flow rates (>0.2 L/min), gas temperatures close to room temperature have been measured by means of micro-thermocouples. The cold plasma was found to be a source of ozone as measurements of the ozone concentration using absorption spectroscopy at the mercury lamp wavelength (253.7 nm), and iodometric titration show. At an air flow rate of 0.4 L/min, we found >1000 ppm ozone in the exhaust stream. Besides serving as an ozone source, the cold plasma jet has the potential for applications such as surface treatment of organic and other heat sensitive materials, and plasma surgery.