Multi-Pronged Applications of RF Sheath and Ponderomotive Force Modeling with the Time-Domain Plasma Model in Vorpal/VSim*

We review results from the study of plasma equilibrium modifications by RF Ponderomotive forces, using coupled Vorpal (FDTD EM+plasma) and UEDGE (2D edge transport) codes.  A bifurcation was observed in the behavior, where low density scenarios push plasma out, exacerbating the low density, while high density scenarios pull plasma in, raising the density.  Also, new work involving RF rectified sheaths, for two different applications, has been done.  Coupling with Univ. of Ill’s plasma-material interaction codes [hPIC2/F-TriDYN/RustBCA /GITR] has been improved, including creation of tools to reduce the size of the surface triangulations from the time-domain code.  We are also using RF rectified sheaths for the study of convective cell behavior in the vicinity of the RF antenna.  Here the same rectified sheath potentials provide boundary conditions for the plasma potential solve, in the equilibrium and turbulence codes [UEDGE/HERMES].  Also, we continue to make improvements to our existing RF sheath model, particularly addressing the modeling of surfaces aligned with the magnetic field, with ion gyro-radius sheaths instead of Debye sheaths, especially in high field regimes.