High-density operation of the Proto-MPEX High Intensity Plasma Source*

The Prototype Materials Plasma Experiment (Proto-MPEX) is a linear high-intensity RF plasma source that combines a high-density helicon plasma generator with ion and electron heating sections. It is being used to study the physics of heating over-dense plasmas in a linear configuration with the goal of delivering a plasma heat flux of \textasciitilde 10 MW/m$^{\mathrm{2}}$ at a target. The helicon plasma is produced by coupling 13.56 MHz RF power at levels of \textgreater 100 kW. A \textasciitilde 30 kW ion cyclotron antenna has recently been installed, and microwaves at 28 GHz (\textasciitilde 150 kW) are coupled to the electrons in the over-dense helicon plasma via Electron Bernstein Waves (EBW). High plasma densities near the target have been produced in D (\textasciitilde 5 x10$^{\mathrm{19}}$/m$^{\mathrm{3}})$, and electron temperatures range from 3 to \textgreater 10 eV, depending on the source parameters. IR camera images of the target plate indicate plasma heat depositions \textgreater 10 MW/m$^{\mathrm{2}}$ for some operating conditions. Details of the experimental results of the operational domain with respect to T$_{\mathrm{e}}$ and n$_{\mathrm{e}}$ as well as results from initial plasma material interaction tests will be presented.