Plasma-Facing Thermal-Protection Loop

L1 watches plasma-facing surface temperatures and acts fast to keep the breeder wall/divertor and burner collectors inside their thermal limits.

Protecting the surfaces

Plasma-facing components — the breeder first wall and divertor, the burner expander and collectors — take intense, sometimes transient heat. If a surface approaches its thermal limit, action must be immediate. L1 runs a thermal-protection loop that senses surface conditions and actuates to reduce load before damage, at protection priority.

Sensing

Surface and near-surface temperatures are inferred from thermal diagnostics (infrared and embedded sensors) and correlated with the heat-flux estimate from the power balance. A fast rise in surface temperature, or a hot spot exceeding a spatial threshold, triggers the loop. Because the response must beat the thermal time constant of a thin surface layer, the sensing-to-action path is engineered fast and deterministic.

Actions

• Impurity seeding / detachment to radiate power off the target.
• Strike-point sweeping (breeder) to spread the load.
• Fast power reduction (beam notch, current/plug adjustment).
• Escalation to controlled shutdown if limits cannot be held.

The loop matches action to severity, like the other graded-protection systems: mild hot spots get seeding and sweeping; severe excursions get power reduction. This keeps the machine operating through routine load swings while guaranteeing the surfaces are never driven past their limits.

Both machines

On the breeder the loop guards the divertor and first wall and works with edge-regime and divertor control; on the burner it guards the expander and DEC collectors, coordinating with DEC ride-through. In both, thermal protection is a fast L1 loop, independent of any model for its limiting action.