REBCO Magnet Command Interface

The command path to the REBCO coil supplies carries current-ramp trajectories under hard slew and field-envelope limits, revalidated at the FPGA edge.

What the interface drives

Both machines use high-temperature REBCO magnets: the breeder to reach 16.84 T peak field (8 T on-axis) and hold the negative-triangularity equilibrium; the burner to reach the 26.49 T plug and 17 T throat. The command interface delivers current setpoints and ramp rates to each coil's power supply, never a raw voltage.

Command structure

# per-coil command frame (L3 -> L1)
cmd = { 'coil_id': k,
        'I_target': I_k,        # A
        'dIdt_max': slew_k,     # A/s, clamped at edge
        'ramp':     traj_k }    # optional shaped trajectory
# L1 edge revalidation before it reaches the supply
assert I_k <= I_limit[k]
assert slew_k <= dIdt_limit[k]
assert field_envelope_ok(I_vector)   # cross-coil peak-field check

The cross-coil field-envelope check is essential: individual coil currents can each be legal while their combination exceeds the local peak-field limit on a conductor. This check runs at the L1 edge because it must complete before any supply acts.

Interface owner and timing

• Owner: L1 control plane (shape and stability loops in ms; protection in µs).
• Sense side: coil current transducers, plus the strain/thermometry interface.
• Protection: co-resident with the quench-detection interface, which can pre-empt any command.

Setpoints originate in the breeder shape MPC or burner plug controller, but the magnet interface treats them as advisory: a quench trip or field-envelope violation overrides intent immediately. This is a design-and-simulation specification; the supplies are exercised against the twin before hardware commissioning.