Modeling and Characterization of Plasma Tubes as Building Blocks for Reconfigurable and Programmable Metasurfaces

Reconfigurable and programmable metasurfaces require reliable strategies for dynamic control of their electromagnetic response. Among the approaches explored so far, low-temperature plasma is particularly attractive thanks to its tunable permittivity, which can be adjusted in real time via electron density modulation. Despite this potential, quantitative experimental validation at microwave frequencies has remained limited. In this work, we present a comprehensive characterization of plasma tubes as reconfigurable building blocks for metasurface architectures. Using a custom waveguide measurement setup, we retrieve key plasma parameters–such as electron density and plasma frequency–under varying excitation conditions. These measurements are complemented by multiphysics plasma simulations, full-wave electromagnetic modeling, and circuit-level electrical diagnostics, ensuring cross-validation across independent methodologies. Our results demonstrate a continuous and controllable tunability of the plasma response, with electron densities reaching the (Formula presented.) range. The close agreement between experiments, models, and simulations confirms the feasibility of integrating plasma elements into adaptive metasurfaces. This study establishes plasma tubes as viable dynamic meta-atoms, paving the way toward high-power, high-speed, and fully reconfigurable microwave systems.