Public domain image - Credit: NASA, S. Gezari (The Johns Hopkins University), and J. Guillochon (University of California, Santa Cruz)

Written by Tim Lash, Focus Fusion Society Contributor

New research results support the predicted performance of ITER. Good news for those diligently constructing the massive reactor in southern France. In plasma, electrons separate from their nucleus leaving behind ions. To continue heating plasma to fusion temperatures requires injecting more energy via radio frequency (RF) waves. Free electrons and ions respond to these waves differently leading to different temperatures for both plasma constituents. Scientists needed to better understand how these differences influence overall plasma temperature and density.

The combination of temperatures within the plasma produce “multi-scale” turbulence. Turbulence can reduce fusion reaction rates. The scientists used a “reduced physics” computer model called TGLF. This model simplifies the massively parallel and costly simulations of multi-scale turbulence that require millions of hours of computing time on supercomputers. These longer running simulations go by the name gyrokinetic multi-scale turbulence simulation. Such complex runs were performed by a similar team as previously noted by

The current research ran this simplified TGLF model hundreds of times on Princeton Plasma Physics Laboratory (PPPL) computers. The model looked specifically at the impact of electron heating on the overall heating mix. Reactors produce such heating by aiming microwaves at the electrons gyrating around magnetic field lines. This microwave process increases the thermal energy of the electrons, transfers it to the ions through collisions and supplements the heating of the ions. Results indicated that studying multi-scale turbulence will be essential to understanding how to deal with the multi-scale effect on the transport of heat, particles and momentum in next-generation tokamaks, or fusion devices.

Of course all tokamak reactors must cope with turbulence from plasma instability. Rather than fight turbulence, the LPPFusion team designed their Focus Fusion 1 reactor to use and leverage plasma instabilities. This simplifies their path to fusion power.