https://phys.org/news/2018-11-plasmas-fusion-microwaves.html

One way a particle can be kicked out of the fusion device is by interacting with waves. Just as a boat in a lake can be jostled by waves passing by, a particle in a plasma can get a boost of energy from waves moving along the magnetic field used to confine the plasma. In the work here, the waves are called Alfvén waves named after the Nobel Prize winner Hannes Alfvén who discovered them. Such waves are problematic for future tokamak fusion reactors because they make it more challenging to keep the plasma hot and undergoing fusion.

"Controlling these waves helps us hold onto the fast particles that heat fusion plasmas," said Dr. Michael Van Zeeland from General Atomics, who led the research. The international team that carried out this research was composed of more than 30 scientists from across the globe who worked together to develop an approach to keep the waves in check.