Experimental properties of surface wave sustained plasma columns close to and above the atmospheric pressure

Summary Form only given, as follows. The use of electromagnetic surface waves to sustain reproducible plasma columns efficiently over an extremely broad range of operating frequencies has been investigated in the pressure range from 200 to 1500 torr. Under such conditions, both the plasma density and the excitation temperature are radially inhomogeneous, resulting in a constriction of the visible radiation of the plasma to a diameter that is smaller than the tube inner diameter. To estimate the degree of inhomogeneity of the plasma, the diameter of the visible part of the discharge has been determined experimentally, and the axial distributions of electron density, excitation, and rotational temperatures have been obtained. The key parameter of surface-wave-produced plasmas is theta , the average power needed to sustain an electron-ion pair. The influence of the gas pressure, wave frequency (40 MHz and 915 MHz), and tube inner diameter (2 mm and 6 mm) on the value of theta has also been investigated.<>