Pellet-Injector Timing Interface

Deposition depth is a timing problem: the injector's launch trigger must be phased to plasma state within a tight window, so timing is an L1-owned interface.

Why timing is the interface

A pellet launched at the wrong instant deposits its fuel at the wrong radius — too shallow and it ablates at the edge, too deep and it perturbs the core. On the breeder, deposition control is achieved by phasing the launch trigger to the measured plasma state, not by changing the pellet after it leaves the barrel.

Timing chain

# launch-phase scheduling (L1)
t_arrival = t_launch + L_flight / v_pellet     # time of flight
phase     = plasma_phase(t_arrival, twin)      # predicted state
if phase in allowed_window and vac_ok:
    fire_launch(t_launch)                       # PTP-timestamped
else:
    hold_and_retime()

Because the trigger references a predicted arrival phase, the interface depends on the digital twin's short-horizon prediction and on flight-time measurement from a light-gate pair. Jitter in the trigger maps directly to jitter in deposition radius.

Budget and owner

Owner: L1 for the trigger; L3 for the demand that sizes the pellet. The trigger is disciplined by the PTP clock distribution so that flight-time and phase are computed on the same time base. Arrival is confirmed downstream and fed back to calibrate the flight-time model. Design-and-simulation specification; commissioned against the twin before hardware.