Overview of the physics basis for the ARC fusion power plant is the 2026 Journal of Plasma Physics paper in which 📝Jon Hillesheim and nineteen co-authors state the design point for 📝ARC and summarize the four companion analyses beneath it.
The design it describes is ARC V3A: an on-axis field of 11.4 📝tesla, 12.0 megaamps of 📝plasma current, a major radius of 4.62 meters and a minor radius of 1.18. From those, the paper projects roughly 1.13 gigawatts of 📝deuterium–📝tritium fusion power and at least 400 megawatts of net electricity to the grid, from a plant 📝Commonwealth Fusion Systems intends to build in Chesterfield County, Virginia by the early 2030s — the site of its 📝power purchase agreement arrangement with 📝Dominion Energy.
The comparison against 📝SPARC is the fastest way to read it. By design, ARC is roughly two and a half times larger in major radius, carries about 40 percent more plasma current, and runs at slightly lower field — and is projected to produce roughly eight times the fusion power, in fifteen-minute pulses rather than seconds.
None of this has been measured. The overview is a synthesis of modeling: exhaust, disruptions, transport and 📝magnetohydrodynamics each analyzed in a companion paper and reconciled here into one self-consistent operating point. Its value is that it is falsifiable — the design point is published with enough specificity that SPARC's results will either support it or not.
The paper's lineage runs both further back and further forward than the collection it heads. The 📝divertor geometry its exhaust companion assumes was worked out years earlier, in 📝The ARC Divertor Papers of 2018 and 2019. The runaway mitigation coil its 📝disruption companion relies on has its own four-paper development record, 📝The Runaway Mitigation Coil Papers. And the material limits implied by this design point are being tested rather than modeled in 📝ARC Engineering Beyond the Physics Basis, where cryogenic fatigue data for 316 stainless steel and IN718 are laboratory measurements. 📝The ARC Physics Basis (2026) is the pillar that holds the five papers together and places this one among them.
We published ARC's physics before pouring its concrete, and we did it in a journal rather than a deck. When SPARC runs, this is the document that gets checked.