The surfatron launcher is an electromagnetic structure designed to produce surface wave discharges (SWDs). Unlike other launchers like the surfaguide, which is coupled via a rectangular waveguide for high power (kW range), the surfatron is coupled to the microwave power supply via a coaxial cable. This design choice limits the operational power to about 400 W at 2.45 GHz but yields high flexibility, making it extremely suitable for active diagnostics such as Thomson scattering (TS) measurements.
Model Validation Against Experiments
To investigate the effect of increasing pressure on the structure and shape of the plasma, we developed a 2D self-consistent (EM and quasineutral plama, not consistent with EEDF solver) physical model. The model couples electromagnetic wave propagation, transport of charged and neutral species, and detailed argon chemistry. Crucially, the simulation results were compared with experimental Thomson scattering data across different pressures. Important is that the simulations allow us to observe how different behave the plasma when surrounded by the faraday enclosure that represents the surfatron itself ("inside" the surfatron)
Interconnection: Molecular Ions and Gas Temperature
As the operational pressure increases towards the intermediate range (2000–8800 Pa), volume recombination processes become increasingly dominant, comparable in magnitude to ambipolar diffusion. The formation of molecular ions (such as Ar2+) plays a vital role in facilitating these volume recombination events.
The density of these molecular species and the resulting recombination rates are strongly coupled with the spatial distribution of the gas temperature. As the gas temperature rises, it alters both the neutral density profiles and the rate constants of the molecular ion chemistry, preventing the plasma from expanding to the discharge tube walls and causing constriction.
