Plug-Coil Actuation Interface

The burner's end-plug coils must hold 26.49 T; the actuation interface is specified honestly against a coil overstressed 3-3.9x at the design bore.

What the plug coils do

A tandem mirror confines plasma between high-field end plugs. The burner's plugs target 26.49 T with a 17 T throat — the fields that create the magnetic mirror and, with the ambipolar potential, plug the ends. This interface commands the plug-coil currents and reads their electromagnetic and mechanical state.

The stress gate, stated plainly

At the design bore, the required field structure overstresses the plug coil by ~3–3.9× the conductor's mechanical limit — it is infeasible as specified. This is a design-and-simulation finding, not a solved engineering problem, and it is not softened here. The actuation interface is documented so the constraint is explicit to any layer or agent reasoning about the burner.

# plug-coil command with the honest limit exposed
sigma_hoop = lorentz_stress(I_plug, B_local, geom)
margin = sigma_allow / sigma_hoop
assert margin >= 1.0, f'plug overstress {1/margin:.1f}x'   # 3-3.9x as specified
plug_supply.command(I_plug, dIdt_max)   # gated by the assertion above

Owner and sensing

• Owner: L1 for the current loop and protection; L3 for the plug-field setpoint.
• Sense: coil current, local field, and the strain/thermometry that quantifies the overstress.
• Protection: shares the quench-detection interface.

Because the coil is overstressed as specified, any hardware path is contingent on a redesign that closes this gate; the interface exists in the design study to make that requirement measurable, not to imply it is met.