Scattering singularities of a resonant cavity containing plasma

The influence of plasma on the evolution of scattering singularities in microwave cavities remains largely unexplored, despite its importance for controlling reflectionless plasma excitation. In this work, we investigate the evolution of scattering singularities in a plasma-loaded microwave cavity. To analyze this complex interaction, a numerical model describing an experimental cavity containing a plasma tube is developed. This model enables the tracking of singularity evolution across various plasma configurations and explains the underlying physical mechanisms. Our results demonstrate that significant changes in the imaginary frequency of these singularities occur under two specific conditions: high collision frequency associated with optimal electron densities or high electron densities associated with optimal collision frequency. Furthermore, in the collisionless regime, we show that the variation of the real frequency increases due to the excitation of a transverse plasmonic resonance inside the plasma tube.