Preliminary Results from the NRL Plasma Surface Wave Test Setup*

A radiofrequency plasma source has been constructed to investigate the propagation of surface waves and currents along a cylindrical column of plasma. The source consists of a argon filled simple glass tube with a short solenoidal antenna wrapped around the exterior. The antenna is connected to a variable power and frequency RF power supply for ionizing the plasma, while secondary broadband antennas are used to excite the surface waves. Measurements of phase changes over broad frequency ranges and spatial distances are used to numerically construct dispersion relations for surface wave modes, which are compared against electron density values inferred from Langmuir probe measurements and microwave interferometry. Preliminary results on transmission properties for different surface modes will also be presented.