Kinetic and Profile Control
Kinetic control shapes the radial profiles of temperature, density, and rotation rather than just their scalar averages.
Beyond scalar control
Early plasma control regulated scalar quantities: total current, average density, stored energy. Kinetic or profile control goes further, regulating the shape of the radial profiles. Performance and stability depend not only on how much pressure a plasma holds but on how that pressure is distributed, so profile control is essential for advanced operation.
The profiles that matter
- Temperature profile, set by heating deposition and transport
- Density profile, set by fueling location and particle transport
- Current profile, set by current drive and resistive diffusion
- Rotation profile, set by momentum input and transport
The estimation challenge
You cannot control what you cannot see. Profile control needs real-time estimates of the full radial profiles, which are reconstructed by combining several diagnostics through a model. The estimation must run inside the control cycle, so reduced models and fast mappings replace slow, high-fidelity codes.
Actuator localization
Shaping a profile requires actuators that deposit their effect at a chosen radius. Neutral beams, electron cyclotron waves, and pellet injection all have controllable deposition locations. Profile control is largely the art of placing these deposits so the profiles relax toward the desired shape as transport carries the effects around.
In the Kronos program
The Hyperion breeder relies on profile control to hold the pressure and current profiles that keep it stable near its operating point at a gain of 3.424. Temperature, density, and current-profile loops are designed to work together, since acting on one changes the others through transport. Their coordination is developed in simulation ahead of first plasma.