Plasma sources are used in many different fields from industry to space. A few examples are reported in the following. In the industrial field plasma is used to change surface properties of materials to enhance gluing and coating, to change wettability, modifying materials ( for example skins) from permeable to water proof, to clean surfaces before other industrial processes, to etch semiconductors and as a process catalyst avoiding dangerous chemical products. Plasma is also used to treat waste to inert reactive materials. Plasma is used in several fields to sterilize system and objects. In the medical sector plasmas are used to treat skin illness from burns to cancers. Plasma is used to enhance combustion efficiency, reduce pollution without catalyst, enhance combustion stability, allow cold start of combustors (when relevant as for aeronautic applications) and allow extremely lean combustion (with Oxidizer over flue ration not normally allowed by standard chemical reaction). In the space field plasma is widely used for propulsion.
In the telecommunication field, plasma is starting to be used to enhance metamaterials properties and as antennas. A Gaseous Plasma Antenna (GPA) is a plasma discharge confined in a dielectric tube that uses partially or fully ionized gas to generate and receive electromagnetic waves; GPAs are virtually “transparent” above the plasma frequency and become “invisible” when turned off. A group of GPAs and, possibly, metallic antennas is called a plasma antenna array (PAA). Unlike ordinary metallic antennas, GPAs and PAAs can be reconfigured electrically (rather than mechanically) with respect to impedance, frequency, bandwidth and directivity on time scales the order of microseconds or milliseconds. It is also possible to stack arrays of GPAs designed to operate at different frequencies. A SPA is a PAA endowed with smart Digital Signal Processing (DSP) algorithms that enhances SPA capabilities by: (i) identifying the direction of incoming signal, (ii) tracking and locating the antenna beam on the mobile/target, (iii) beam-steering while minimizing interferences. Plasma sources described above range from low pressure (10-1 mbar) to high pressure (atmospheric).
One of the most advanced and interesting applications is to use an array of gas-plasma sources to build-up advanced antenna systems showing re-configurability and tenability, unachievable with standard units. In all of these applications, and particularly in the telecommunication field, plasma sources need to be compact, high density ( the actual limit not using high power lasers is about 1019 ion/m3), compatible with demanding environment ( high temperature, corrosive ), allow application of different gases and be efficient ( thus using low power). Actual technology is based mainly on: (i) DC discharge, (ii) AC discharge, (iii) RF discharge, (iv) Microwaves, (v) Hollow cathode. Improvement of plasma source performances require a strong effort in term of modelling and technology.
The aim of PATH is to merge European competences to make a substantial step toward innovative hybrid plasma sources based on a combination of the previous technologies. In fact current technology is limited to a density between 1019 and 1020 ion /m3.