Fusion reactor design

Everyone knows that the game of billiards involves balls careening off the sides of a pool table — but few people may know that the same principle applies to fusion reactions. How charged particles like electrons and atomic nuclei that make up plasma interact with the walls of doughnut-shaped devices known as tokamaks helps determine how efficiently fusion reactions occur. Specifically, in a phenomenon known as secondary electron emission (SEE), electrons strike the surface of the wall, causing other electrons to be emitted.

Like a potter shaping clay as it spins on a wheel, physicists use magnetic fields and powerful particle beams to control and shape the plasma as it twists and turns through a fusion device. Now a physicist has created a new system that will let scientists control the energy and rotation of plasma in real time in a doughnut-shaped machine known as a tokamak.

Physicist Fatima Ebrahimi at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) has published a paper showing that magnetic reconnection — the process in which magnetic field lines snap together and release energy — can be triggered by motion in nearby magnetic fields. By running computer simulations, Ebrahimi gathered evidence indicating that the wiggling of atomic particles and magnetic fields within electrically charged gas known as plasma can spark the onset of reconnection, a process that, when it occurs on the sun, can spew plasma into space.