Alcator C-Mod was the compact, high-field tokamak operated at MIT from 1993 to 2016, whose record-setting plasma pressure validated the high-field approach to 📝fusion.
The name contracts Alto Campo Toro — Latin for "high-field torus" — and names a lineage of MIT machines built on a contrarian premise: that a small 📝Tokamak with a very strong magnetic field could match the performance of machines many times its size, because 📝fusion power density rises steeply with field strength. C-Mod, the third Alcator, ran copper magnets at up to 8 tesla — the highest field of any tokamak — in a 📝plasma volume of roughly one cubic meter. In its final run in September 2016, it set the world record for plasma pressure, 2.05 atmospheres — the quantity that most directly determines fusion power output.
Operated as a national user facility by the 📝MIT Plasma Science and Fusion Center, C-Mod also pioneered territory beyond raw field: it was the only machine of its era with all-metal plasma-facing walls and reactor-level heat fluxes on its 📝divertor, and it relied entirely on radio-frequency heating rather than beams — all choices later machines and power-plant designs adopted. The mainstream of fusion research answered the confinement problem with size; the Alcator line answered it with field, and that argument outlived the machine itself.