Shedding light on key physics elements for future D-T plasmas
The path towards commercial fusion reactors, although better understood in recent decades, still faces numerous physical and technological challenges. Fundamental issues such as the optimal size, magnetic configuration, confinement type, and power exhaust techniques for future tokamak devices are not fully established. These uncertainties highlight the need for continued research to establish a safe and clear path toward generating energy efficiently through nuclear fusion, especially in Deuterium-Tritium (D-T) plasmas.
In recent years, the JET tokamak has conducted new D-T experiments, building on the pioneering work done a TFTR and JET in the 1990s. These campaigns achieved high fusion power generation using Neutral Beam Injection (NBI) and Ion Cyclotron Resonance Frequency (ICRF) heating, the primary heating mechanisms at JET. These efforts have explored key features that will likely define future D-T plasmas, including dominant electron heating, low rotation, and fully destabilized energetic ion instabilities.
IPFN researcher Rui Coelho, also affiliated with the Department of Physics and Department of Nuclear Sciences and Engineering at IST, collaborated with a leading team of scientists on these JET campaigns. He is one of the main authors of a paper recently published in Nature Communications.
Their analysis and modelling suggest that the development of large-scale energetic particle (EP) perturbations in the presence of highly energetic ions can substantially reduce conductive-convective energy losses driven by micro-turbulence in the plasma core, resulting in excellent core energy confinement.
The study highlights the critical role of zonal flows, which are non-linearly driven by EP-induced instabilities, in reducing turbulent energy transport under the conditions explored. At these low energy loss levels, there is a notable asymmetry between Tritium (T) and Deuterium (D). Tritium significantly enhances zonal flow activity, further reducing energy losses through transport mechanisms, which leads to superior global confinement in D-T plasmas compared to Deuterium-only plasmas.
These findings pave the way for a more economical and simpler tokamak design, reinforcing the promise of magnetically confined D-T plasmas as a viable source of clean, sustainable energy.