As scientists study approaches to best sustain a fusion reactor, a team led by Oak Ridge National Laboratory investigated injecting shattered argon pellets into a super-hot plasma, when needed, to protect the reactor’s interior wall from high-energy runaway electrons. Other pellet materials, frozen from room-temperature gasses, have successfully reduced the plasma’s thermal energy, but argon was most effective at runaway electron dissipation. Using fuel pellet injection technology – which literally shoots cryogenic pellets of fuel into the plasma to raise its density – the team used an injector optimized for argon during a series of tests at the DIII-D National Fusion Facility. “Now that we have demonstrated argon’s effectiveness, our next step is to determine how many pellets and pellet injectors are needed for a solution that’s applicable,” said ORNL’s Larry Baylor. This research may be scaled up for possible application on ITER, the international experimental reactor.