The report scores how tightly a coil concentrates its field near the center, as the share of the field that sits at or above half the peak.
Where it appears in the report: Field Coverage, secondary field metrics
The evidence
The score is the field at points reaching at least 50 percent of the peak, divided by the total field inside the coil boundary. It's an in-house metric, so we document how it's derived rather than point to an outside standard.
Concentration score asks how much of the field lands in its strongest zone. The gauge on the left is that score as a percentage, the same gauge the report shows. On the right is the field it measures: the core is the region at or above half the peak strength, and the score is the share of the field inside it. A tightly focused coil puts most of its field in the core and scores high; a broad coil spreads it out and scores lower. It describes focus at the surface, not depth.
