Control and Instrumentation
A real-time control system ties diagnostics to actuators, holding the plug potential, density, and temperature within the stable operating band.
Closing the loop
The burner is an actively controlled machine. Its confinement depends on a maintained potential structure, which depends in turn on heating and fueling that must respond in real time to what the plasma is doing. The control system reads diagnostics, compares against targets, and commands the actuators — beams, ECRH, fueling, and power electronics — to keep the machine on point.
What is controlled
- Plug potential and thermal barrier via ECRH and beam power
- Density via fueling rate and pumping
- Ion and electron temperature via heating balance
- Output level for load following, within stability limits
| Diagnostic signal | Actuator response |
|---|---|
| potential low | raise plug ECRH / beam |
| density high | reduce fueling |
| impurity spike | adjust boundary / alarm |
| load rises | increase fuel + heating |
Safety interlocks
The control system also enforces limits: if the plasma approaches a stability boundary or a component nears a thermal limit, interlocks trim the machine back or terminate the burn safely by dumping plasma into the expander. Because the linear machine has no disruption risk, a controlled shutdown is benign — the plasma simply flows out the open ends.
Control performance is central to holding a demanding D-3He burn and to firm, dispatchable operation. The control architecture is developed in the design study and matured on the test unit, where the real plasma response is measured for the first time.
Because the machine's confinement is actively maintained rather than passively topological, control is not a convenience but a core subsystem — the plasma exists in its burning state only as long as the control loop keeps the potential structure standing.