[sam]

We are careful to always specify what kind of “breakeven” or “gain” is being referred to on all graphs and statements about the performance of specific experiments in this paper.

Energy gain (in the general sense) is the ratio of fusion energy released to the incoming heating energy crossing some closed boundary.

The right question to ask is then: “what is the closed boundary across which the heating energy is being measured?” For scientific gain, this boundary is the vacuum vessel wall. For facility gain, it is the facility boundary.