Influence of the dielectric surrounding of plasma on the electron density measurement by microwave interferometer

Using a vector network analyzer a frequency resolved microwave interferometer is built up in the range of 42.5–50 GHz. Due to the frequency resolved measurement technique it is possible to investigate the influence of the surrounding dielectric material on the transmission. The experiments are performed on a fluorescent lamp, which is enclosed by a glass tube. Furthermore, a dielectric resonator is built up by two plane silica windows, placed perpendicular to the beam. It was found that the influence can be described by a one-dimensional model using equivalent circuits, which is in very good agreement with experimental results. In addition, the common technique of rotating the windows to reduce their influence is investigated. (paper)