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​Rotation is key to the performance of salad spinners, toy tops, and centrifuges, but recent research suggests a way to harness rotation for the future of mankind's energy supply. In papers published in Physics of Plasmas in May and Physical Review Letters this month, Timothy Stoltzfus-Dueck, a physicist at the Princeton Plasma Physics Laboratory (PPPL), demonstrated a novel method that scientists can use to manipulate the intrinsic — or self-generated — rotation of hot, charged plasma gas within fusion facilities called tokamaks. 

Such a method could prove important for future facilities like ITER, the huge international tokamak under construction in France that will demonstrate the feasibility of fusion as a source of energy for generating electricity. ITER's massive size will make it difficult for the facility to provide sufficient rotation through external means.

Rotation is essential to the performance of all tokamaks. Rotation can stabilize instabilities in plasma, and sheared rotation — the difference in velocities between two bands of rotating plasma — can suppress plasma turbulence, making it possible to maintain the gas's high temperature with less power and reduced operating costs.

Today's tokamaks produce rotation mainly by heating the plasma with neutral beams, which cause it to spin. In intrinsic rotation, however, rotating particles that leak from the edge of the plasma accelerate the plasma in the opposite direction, just as the expulsion of propellant drives a rocket forward.

On the Tokamak à Configuration Variable (TCV) in Lausanne, Switzerland, Stoltzfus-Dueck and the TCV team influenced intrinsic rotation by moving the so-called X-point — the dividing point between magnetically confined plasma and plasma that has leaked from confinement. 

Read the full article on the PPPL website.

(Images obtained on the TCV tokamak.)