Controlling instabilities called Alfvén waves can lead to higher temperatures within tokamaks and more efficient fusion processes. A number of institutions have recently conducted research, led by Gerrit Kramer at PPPL, that suggests that applying magnetic fields to fusion plasmas can calm these waves. "You want to suppress the Alfvén waves as much as possible so the fast ions stay in the plasma and help heat it," Kramer said.

The team first gathered data from the National Spherical Torus Experiment (NSTX) at PPPL before it was upgraded, and then conducted plasma simulations on a computer cluster at PPPL. The simulations, reported in the journal Plasma Physics and Controlled Fusion, found that externally applied magnetic perturbations can prevent the waves from growing. The perturbations reduce the different velocities of the ions in the plasma as they zoom around the tokamak, calming disturbances within the hot gas.

The simulations further showed that magnetic perturbations can calm Alfvén waves that have already formed. "The plasma absorbs all the energy of the wave, and the wave stops vibrating," Kramer said. Collaborating with Kramer on this path-setting research were scientists from General Atomics, Oak Ridge National Laboratory, the University of California, Los Angeles, and the University of California, Irvine.