PPPL Calculations Identify Heating-First Sequence to Reach Fusion Ignition at Lower Energy Cost

The team led by Luis Delgado-Aparicio extended the classic Lawson criterion by adding four performance factors including impurities and magnetic-field effects. Their analytic model identifies the Cordey saddle as the lowest-energy passage to self-sustaining burning plasma. In contrast to the National Ignition Facility’s 2022 density-then-heat shot that achieved Q greater than 1, the new route prioritizes temperature rise first, avoiding the steepest region of the energy landscape.

Private fusion firms have largely followed the “climb the mountain” strategy of rapid compression followed by massive auxiliary heating. The PPPL route implies that stellarators and high-field tokamaks could reach ignition with smaller heating systems, lowering capital costs. Cross-checks against ITER’s projected Q=10 baseline and recent SPARC magnet data suggest the Cordey passage remains accessible even with realistic impurity levels.

The work remains purely computational; no new hardware has been tested. A decisive next step would be a dedicated heating-compression experiment on an existing device such as NSTX-U or a private stellarator to measure actual Q at the predicted saddle point. Without such validation the energy savings remain theoretical.