Full-wave theory of a quasi-optical launching system for lower hybrid waves: the step density case

Numerical studies on the use of a quasi-optical grill to couple lower hybrid waves to a plasma, for current drive in tokamaks, are currently under way. Study of the coupling has been carried out in a rigorous way, through the solution of scattering from cylinders with parallel axes in the presence of a plane of discontinuity for electromagnetic constants. Here we restrict our attention to the case of a plasma with a step density profile and report some results on launched spectra, coupled power and directivity.