Radio frequency plasmas in pure water within hole in insulating plate

RF plasmas in pure water (similar or equal to 0.2mS/m) can be generated within a hole in an insulating plate, apart from the electrodes. When the diameter of the hole is 3-10 mm, the plasmas can be maintained stably. The existence of bubbles in the hole is important for the generation of plasmas. In the results of spectroscopic measurements, only the lines from the atoms (O, H) and molecule (OH) derived from H2O molecules were observed. (C) 2015 The Japan Society of Applied Physics