Surface wave in a plasma column: dipolar wave

The dispersion characteristics of the dipolar mode (m = 1) have been measured in a plasma waveguide consisting of a circular waveguide coaxial with the positive column of a mercury discharge. A theoretical study of this mode has been made assuming that the plasma was an homogeneous dielectric medium, and taking into account the thickness and the dielectric constant of the surrounding glass and also the diameter of the metallic waveguide. Good agreement between the theory and the experimental results was found. On the basis of this, it can be assumed that it is not necessary to consider the density gradient along the radius of the plasma in order to study this mode.