A computer modelling and its partial experimental validation to study the attenuation of electromagnetic waves in plasma using CST MICROWAVE STUDIO®

There is a huge interest among the scientific fraternity to generate plasma that can selectively absorb or reflect the incident microwaves. Simulations have been carried out to study the absorption of microwaves in plasma using plane wave as a source. In real experiments, the source of microwaves is not always a plane wave and hence the exact simulated replication of the experiment cannot be done using a plane wave source. In order to generate the exact experimental conditions, a horn antenna has been designed and used as a source. A computer model to study the attenuation of X-band (8-12) microwaves in a plasma medium is prepared and partially validated using suitable initial experiments. The study can be extended to any target microwave frequency band. The present work discusses the preliminary simulations that are carried out to study the effect of plasma frequency (omega p) and collisional frequency (upsilon c) on attenuation of microwaves (MW) of 8-12 GHz using CST (R) MWS (R). The plasma is treated as a Drude dispersive material whose properties are governed by two plasma parameters, namely plasma frequency (omega p) and collisional frequency (upsilon c). The simulation is carried out on an array of plasma tubes enclosed in a housing made of teflon. This chamber is then illuminated with microwaves using a horn antenna unlike other simulations where the source of the signal is a plane wave. Using a horn antenna as the transmitter and receiver allows exact simulation of the experimental conditions in the laboratory. The amount of attenuation is measured by considering the difference in return losses with and without plasma. The attenuation of incident microwave is studied by varying plasma frequency from 0.02 GHz to 3 GHz at a fixed collisional frequency of 1010 S-1. The simulation is also carried out by varying upsilon c from 108 to 1011 S-1 at a constant omega p. An experiment to validate the simulation is designed to validate the simulation results. For experimental purpose, fluorescent tube array (FTA), which is a series connection of commercially available tubes is excited using a high-frequency power supply of suitable voltage. The simulation and initial experimental results are compared and are in good agreement with each other. This model serves as a tool to study the attenuation of MW in plasma with given omega p and upsilon c well before the experiment is carried out. This can also be used to select optimum working points for further experiments.