Full-Wave ICRF Codes
Full-wave codes solve Maxwell's equations in the plasma for ion-cyclotron waves, capturing interference and mode conversion that ray-tracing cannot.
When rays are not enough
Ion-cyclotron range-of-frequency (ICRF) waves have wavelengths comparable to plasma gradient scales, so the geometric-optics assumption behind ray-tracing breaks down. Full-wave codes instead solve the wave equation, derived from Maxwell's equations plus a plasma dielectric response, over the whole domain, capturing diffraction, interference, and boundary effects.
The dielectric response
The plasma enters through a hot-plasma conductivity or dielectric tensor that depends on the particle distributions and the wave frequency relative to the ion-cyclotron harmonics. This tensor is non-local in space, which makes the full-wave problem large and dense, and demands careful numerical treatment.
Mode conversion
In multi-species plasmas, a fast wave can convert to a slower wave near ion-ion hybrid layers, depositing power through a different channel. Mode conversion is inherently a wave-interference phenomenon that only full-wave codes represent, and it can be used deliberately to heat or drive flow in specific regions.
Inputs and outputs
- Inputs: antenna geometry and spectrum, equilibrium, and species profiles
- Outputs: two- or three-dimensional wave fields, power deposition by species, and antenna loading
Coupling to distributions
ICRF often creates energetic minority-ion tails, so full-wave codes are coupled to Fokker-Planck solvers to compute the non-Maxwellian distribution self-consistently, since that distribution in turn changes the wave absorption. The iteration between field and distribution is a defining challenge of ICRF modeling.
Full-wave analysis is the rigorous tool when a heating scheme relies on interference or conversion physics that a ray picture would miss.