Neutral-Beam Injector Interface

The neutral-beam interface delivers heating, current drive, and fueling with a fast-notch protection path that can blank the beam within microseconds.

What the beam does

On the breeder, neutral-beam injection (NBI) delivers auxiliary heating and a fueling contribution while helping shape the current profile that supports the negative-triangularity equilibrium. The interface commands beam power, energy, and on/off timing, and hosts a fast protection notch.

Command set and protection

• Actuate: source current/voltage (power), modulation gate, aiming (where steerable).
• Sense: beam current, shine-through, duct thermocouples, calorimetry.
• Protect: fast notch that blanks the beam on a fault trigger.

# fast beam notch (L1 protection)
if shinethrough > s_max or duct_T > T_max or disruption_precursor:
    beam_gate.notch()          # blank in us, keep source alive
# resume only when cause clears and supervisor re-arms
if cause_cleared and rearmed:
    beam_gate.restore(power_ref)

The notch is distinct from a shutdown: it removes beam power in microseconds while keeping the source conditioned, so heating can resume as soon as the fault clears. Shine-through protection guards the far wall when target density is low.

Owner and timing

Owner: L1 for the notch and power loop; L3 sets the heating/current-drive reference as part of the scenario. The notch trigger can come from a disruption precursor supplied by the twin, but the blanking action itself is hardware-fast and independent of the learning path. Calibration ties source settings to delivered power via calorimetry. Design-and-simulation specification, validated against the twin before commissioning.