Researchers Discover New Ways to Improve Plasma Control Using Supercomputers

Researchers from General Atomics and the University of California San Diego used CGYRO gyrokinetic code on the Frontier supercomputer in the Oak Ridge National Laboratory for multiscale simulation of plasma temperature fluctuations driven by turbulence making a breakthrough in plasma retention. The conclusions of the team will help to optimize the design of future tokamaks.

Plasma retention in fusion plants (tokamaks) is limited by small but steady heat loss caused by turbulence. One important method to improve tokamak confinement is a byproduct of the commonly used neutral beam injection that uses an intense particle beam to heat the plasma to 150 million degrees Celsius. 

It was considered that except heating, the beam also causes the plasma to rotate around the tokamak’s chamber, which is believed to improve the quality of confinement. However, a new study conducted on the Frontier supercomputer at the Department of Energy’s Oak Ridge National Laboratory revealed important exceptions to the rule on plasma rotation in tokamaks. According to Emily Belli, a physicist at General Atomics in San Diego and lead author of the paper, the plasma edge region is really important because it sets the global confinement of energy and heat in the plasma, but calculating the turbulence in this edge region is very difficult. To do this, one must capture the subtle interaction between very heavy ions and very light electrons. Previous simulations in this edge region were limited computationally and could only have the ion physics or only have the electron physics, and it was impossible to describe the complex interplay between the two. However, now this became possible with Frontier.

The team of researchers modeled the impact of plasma rotation on both types of particles. Considering the interaction between ions and electrons, rotation can increase the general level of turbulence, which subsequently reduces the quality of confinement. 

The research will help to improve the control over plasma and tokamak confinement, which will contribute to using fusion for commercial purposes.