Every gain figure
carries its denominator.
A directory of fusion and advanced-nuclear organisations whose spine is a sourced benchmark of what each device has actually achieved — and an explicit statement of what each number means.
Both figures are true. Why that matters.
The problem, in one example
In December 2022 the National Ignition Facility reported a fusion gain of 4.13. The figure is accurate — it counts the laser energy delivered to the target. Measured instead against the ~400 MJ the facility's capacitor bank stores for each shot, the same result is 0.0077, and the true wall-plug figure is lower still, because that 400 MJ excludes cooling, controls and cryogenics.
Neither number is dishonest. They answer different questions, and reporting slides between them constantly. So this site has no field in which an undenominated gain could be stored — and it holds itself to the same rule, which is why the sentence above says what the 400 MJ does and does not cover. See both figures.
Every number states what it is
Each figure carries its status — achieved on a shot, claimed by its source, or planned as a target. Targets never enter a ranking, and design specifications are held apart from results, so a machine's brochure figure is never presented as something it has done.
We also publish what this dataset does not know — including that 11 of 446 measurements have been checked against a primary source. See coverage, or download the data.