Dan Brunner is a 🏷️#physicist and a 🏷️#founder of 📝Commonwealth Fusion Systems, named the company's chief technology officer when it launched out of the 📝MIT Plasma Science and Fusion Center in March 2018 alongside 📝Bob Mumgaard and 📝Brandon Sorbom. He earned his doctorate at MIT in 2013, and his experimental subject is how much of a tokamak's exhaust power arrives, and over how narrow a strip.

That strip is the 📝scrape-off layer heat flux width, λ_q, and it decides whether a 📝divertor survives. Brunner is lead author of the 2018 Nuclear Fusion paper that measured it on 📝Alcator C-Mod at poloidal fields up to about 1.3 📝tesla — reactor-level, and roughly 50 % above the ceiling of the international database that preceded it, since C-Mod was the only diverted tokamak that could reach there. The result, written with 📝Brian LaBombard, 📝Adam Kuang and James Terry, was that λ_q collapses onto a single dependence across confinement regimes: in 📝L-mode, I-mode and 📝H-mode alike it varies as the inverse square root of volume-averaged core pressure, to within about 20 %. Those are measurements, taken on a machine that has since been shut down, and they are among the inputs that size the exhaust problem for 📝SPARC and 📝ARC. Brunner also co-authored the 2023 design paper for the pair of high-field 📝REBCO end coils CFS built for a 📝magnetic mirror device, and a 2024 analytical method for force-balanced tokamak magnets.