Radio-Frequency Heating

Radio-frequency systems couple energy to the plasma at resonant frequencies, providing targeted, wall-clean heating and profile control.

Radio-frequency (RF) heating delivers power by launching electromagnetic waves that the plasma absorbs at a resonance — for ions, near the ion-cyclotron frequency set by the local field. Because the field varies along the axis, the resonance can be placed where heating is wanted. RF complements neutral beams: it needs no line-of-sight fast-atom source and can be aimed at specific regions of the plasma.

In the burner, RF can heat the central-cell ions, tailor the plasma profile, and contribute to sustaining the plug plasma. Antennas or launchers sit at the vessel wall and couple power across the plasma edge, so their design must handle the edge plasma and the loads there without introducing impurities.

Why include RF

• Place heating at a chosen axial location via the resonance
• Heat ions or electrons depending on frequency and scheme
• Provide profile and control authority separate from beams
• Avoid a large line-of-sight injection duct
• Support startup and plug sustainment

Constraints

RF coupling degrades if the edge plasma conditions drift, and antennas near the plasma are exposed to heat and particle flux that can erode them or sputter impurities into the plasma. Impurity control matters because high-Z impurities radiate strongly and cool the plasma. The RF systems are designed with these edge-interaction limits in mind, and their reliability contributes to the overall availability picture.

All figures are design-and-simulation values for a machine not yet built.