A novel path to fusion ignition: heat first, then add fuel

[Marlin]

A novel path to fusion ignition: heat first, then add fuel

https://www.pppl.gov/news/2026/novel-path-fusion-ignition-heat-first-then-add-fuel

[Core Content]

Illustration fusion ignition artist's rendering

Physicists at the Princeton Plasma Physics Laboratory have reformulated the traditional Lawson criterion for fusion ignition. The updated model maps an energy-efficient path that requires heating the plasma before increasing its density.

This theoretical framework helps researchers evaluate tokamak and stellarator designs by incorporating real-world factors like wall impurities and energy losses. Better operational planning could lower development costs and reduce thermal instability risks for future commercial fusion power systems.

For more than 70 years, fusion energy researchers have used a particular equation to judge whether a plasma would stay hot and dense enough — for long enough — to reach a point where it could sustain itself without any more external power added. While that equation marks the finish line, also known as ignition, it says nothing about the best way to

The original "ideal" equation, known as the Lawson criterion, was first developed in the 1950s. Now PPPL physicistsLuis Delgado-Aparicio,Masayuki Ono andJonathan Menard have reformulated that ideal criterion while adding four other conditions for reaching and holding a burning plasma to plan the best process for heating and powering the plasma within a fusion energy system. Their work waspublished Link is external in the journal Physical Review Letters.

Read the full article at pppl.gov:
https://www.pppl.gov/news/2026/novel-path-fusion-ignition-heat-first-then-add-fuel