A fusion reactor in San Diego surpasses a limit on plasma density.

Right now, the goal for ITER is Q=10 which means making 10 times the energy it needs to run. The plan to achieve this involves using a plasma current reaching over 15 MA. “One problem with 15 MA is that you have very large [instabilities called] ELMs that can melt the wall,” Garofalo said. “The other problem is that there is increased probability of plasma collapsing very quickly and damaging the machine—we call that disruption. Our scenario reduces the plasma current, which makes the ELMs smaller, makes the probability of the disruption smaller, and makes the consequences of disruption more benign. It’s potentially a safer path to this Q=10 goal.”