A plasma applicator includes a plasma discharge tube and a microwave cavity at least partially surrounding a portion of the plasma discharge tube. Microwave energy is coupled to the microwave cavity via a coupling iris. At least two orthogonal dimensions of the microwave cavity are selected such that the microwave energy in the microwave cavity propagates in a transverse electric (TE) mode. Primary electric fields generated from the microwave energy combine with an evanescent electric field generated from the coupling iris, such that a combined electric field in the microwave cavity is substantially uniform along the longitudinal axis of the plasma discharge tube. A plurality of radial microwave chokes is disposed over an exterior of the plasma discharge tube. Positions of the microwave chokes are such that microwave energy propagating in the TE mode and a transverse electric magnetic (TEM) mode is attenuated.