Study of a New Plasma Source for Free‐Standing Plasmas

A new type of plasma source to maintain a free-standing, linearly extended plasma was studied. The plasma reactor is a microwave concentrator which is comprised of a cylindrical cavity with an elliptical base and a microwave antenna near one of its focal lines and is operated at f = 2.45 GHz. Numerical simulations and measurements of the microwave pattern inside the assembly were found to be in good agreement with each other. Electron densities and electron temperatures were measured using Langmuir probes. A completely free-standing plasma inside an evacuated glass tube was achieved for certain combinations of gas pressure and injected power.