RF Full-Wave Codes
Full-wave codes solve the Maxwell wave equation in the plasma directly, capturing interference, mode conversion, and short-wavelength effects ray tracing omits.
When rays fail
Geometric optics assumes the wavelength is short compared with plasma gradients. For ion-cyclotron and some hybrid waves this fails: wavelengths are comparable to the antenna and to plasma structures, and phenomena like interference, cutoffs, and mode conversion between wave branches dominate. Full-wave codes abandon the ray picture and solve the wave equation, Maxwell's equations with the plasma dielectric response, throughout the domain.
The result is the full electromagnetic field, from which power absorption is computed exactly, including at mode-conversion layers where energy transfers between fast and slow wave branches.
The numerical problem
Solving the vector wave equation on a two- or three-dimensional grid with the anisotropic, spatially varying plasma dielectric tensor yields a large complex linear system. The plasma response is nonlocal in the ion-cyclotron regime, which couples grid points across the finite Larmor orbit and complicates the matrix structure.
Antenna coupling
Full-wave codes naturally include the launching antenna as a boundary condition, so they predict how well an antenna couples power into the plasma, a question ray tracing cannot address. This makes them essential for ion-cyclotron antenna design.
Design relevance
Where the Hyperion breeder heating scheme uses waves in regimes where geometric optics is invalid, full-wave modeling predicts absorption and antenna coupling more faithfully than ray tracing. Coupled to a Fokker-Planck solver it yields self-consistent heating and current-drive profiles, all in simulation.
- Solves Maxwell's wave equation in the plasma
- Captures interference, cutoffs, mode conversion
- Includes antenna coupling as a boundary condition
- Essential in the ion-cyclotron regime