Campaign Lifecycle and Duty Cycle

How individual shots accumulate into a campaign, and how duty cycle sets the ceiling on breeder availability and tritium output.

From shots to a campaign

A campaign is a planned series of shots run against fixed hardware between maintenance openings. Availability at campaign scale is bounded by duty cycle: the ratio of productive flat-top time to the full arm-to-recovery period, multiplied by the fraction of calendar time the machine is in-campaign rather than in maintenance. For the breeder this directly sets annual tritium output toward the ~4 kg/yr class and helium-3 toward ~1.97 kg/yr.

def campaign_availability(flattop_s, cycle_s, shots_per_day, up_days, cal_days):
    duty = flattop_s / cycle_s                 # in-shot productive fraction
    daily_prod_s = duty * cycle_s * shots_per_day
    seconds_per_day = 86400.0
    in_shot_frac = daily_prod_s / seconds_per_day
    calendar_frac = up_days / cal_days         # campaign vs maintenance
    return in_shot_frac * calendar_frac

What limits duty cycle

• Thermal recovery of plasma-facing components between shots
• Coil recooling and current-supply recharge windows
• Vacuum and wall reconditioning after high-power shots
• Diagnostic and data-capture overhead in recovery
• Scheduled inspection openings that end a campaign

Duty cycle vs availability

Duty cycle and availability are related but distinct. A machine can be highly available (rarely broken) yet low duty cycle (much time spent recovering between shots). The predictive-maintenance layer works to convert unplanned campaign-ending faults into scheduled openings, protecting both. See Predictive Maintenance and Availability Modeling.

At fleet scale the FOAK-NOAK-BOAK breeder sequence (from ~2030) is expected to raise duty cycle as each unit inherits validated recovery procedures. Pre-FOAK, campaign models run against the twin to size the recovery budget honestly rather than optimistically.