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

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 reach it. New research from the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) maps a path to ignition conditions using far less energy than any other path.