Disruption Avoidance
Acting on early warning to steer the plasma away from a disruption while keeping the discharge alive.
Avoid before you mitigate
Mitigation limits the damage of a disruption; avoidance prevents it. Avoidance is always preferable because it keeps the plasma useful. When the predictor and physics indicators show the plasma approaching a limit, the avoidance logic applies controlled changes that increase margin without terminating the discharge.
Levers of avoidance
- Reduce fueling or heating to back away from a density or beta limit
- Adjust shape or current to raise stability margins
- Apply targeted current drive to control tearing modes
- Increase rotation or apply error-field correction to stabilize modes
- Soften the planned trajectory - flatten a ramp, delay a step
Graded response
Avoidance is graduated. Early, gentle warning triggers small corrections that a human would barely notice. As proximity grows, the response escalates: larger corrections, then a controlled ramp-down, and only if avoidance fails does the stack hand off to mitigation. Each escalation step is pre-validated so it does not itself create a new problem.
The trade against false alarms
Aggressive avoidance that fires on weak signals wastes discharges and erodes trust; timid avoidance that waits for certainty acts too late. Tuning this trade - the operating point on the alarm-versus-miss curve - is a core design decision, made explicit rather than buried in a threshold.
Where avoidance meets scenario control
Avoidance actions are implemented through the same actuator-management and scenario layers as normal control, using pre-validated alternate branches. This reuse means an avoidance maneuver is a known, tested trajectory, not an improvised command issued in a crisis.