Investigation on advanced materials of plasma sources for plasma antenna applications

Gaseous Plasma Antennas are devices which rely on a partially or fully ionized gas to radiate EM waves, thus differing from the traditional antenna design that is based on metallic wires and/or surfaces. Gaseous Plasma Antennas consist of dielectric vessel filled with a neutral gas such as argon that is energized by any generation method to form plasma. A metal circuit is wrapped around the tube or in contact with the plasma itself to inject the signal frequency into the plasma. Plasma antennas might offer several advantages with respect to conventional antennas, e.g. electrical frequency reconfigurability, making them suitable for space communications. The plasma antennas performances, e.g. gain, are related to the discharge parameters, in particular the plasma density is the parameter on which this work is focused on. In this study, the use of different materials to increase the plasma density, and consequentially the antenna gain, is investigated. The external casing of the plasma sources is made of glass. To improve the electron density value of a Gaseous Plasma Antenna in the same working conditions, many attempts have been made in replacing or coating the glass with different materials. These materials are characterized by a high value of Secondary Electron Emission Yield. The Sol-Gel method is used to make a thin film and the procedures to realize the coatings are described. The Scanning Electron Microscope images and the profilometer analysis to investigate the morphology and the thickness of the deposited layers are shown. By means of a microwave interferometer, the plasma density is measured. Data analysis and results of the experiments are presented, showing that the materials derived from the literature are indeed applicable to plasma antennas to increase the plasma density.