File:Atmospheric-pressure plasma.jpg

English: The image depicts an atmospheric-pressure non-equilibrium plasma based on a dielectric barrier discharge (DBD) in the lab. Inside the DBD is a steel inner electrode surrounded by a concentric copper ring outer electrode, which are separated by a glass capillary (the dielectric). A high voltage alternating current (2-3 kVpp, 20-50 kHz) is applied between the electrodes. Helium flows through the inner electrode and forms a plasma jet. The plasma is initially formed between the inner electrode and the glass capillary in the region where the electrodes overlap. The color of the plasma is a bright UV blue close to the region of plasma formation, but forms a purple stream outside of the glass capillary. The color differences are due to the different reactive species formed from either helium from the gas supply or nitrogen in the atmosphere.