China nuclear fusion discovery finds mysterious energy boost to power up plasma

collaborative effort between researchers at the Shanghai Jiao Tong University and the Chinese Academy of Sciences led to the deployment of a simulation code on a nuclear fusion collision model that has unlocked the physics behind supra-thermal ions in the burning plasma.

EAST fusion-research tokamak at the Chinese Academy of Science’s Institute of Plasma Physics (ASIPP) in Hefei, China.

This helps us improve our understanding of how nuclear fusion reactions occur and how they can be improved.

In our bid to transition to clean energy, nuclear fusion is a critical component. Replicating reactions that power the Sun here on Earth could help us unlock boundless energy without emitting planet-warming gases. To reach there, we need to first succeed in getting more energy out of a nuclear fusion reactor than we put in.

Humanity made some progress in this direction when the US’s National Ignition Facility (NIF) achieved a net gain of 3.15 million Joules (MJ) of energy in December 2022. To make further advances, scientists are, however, focusing on another NIF milestone achieved in February of 2021 – burning plasma for the first time.

What is burning plasma?

In NIF’s approach to harnessing fusion energy, a fuel mix of deuterium and tritium (DT) undergoes implosion under reaction conditions similar to what exists in the stars. NIF refers to this approach as inertial confinement fusion (ICF).

In ICF, when deposited energy from alpha particles is more than required for achieving implosion, the reaction mix enters a burning state that amplifies energy densities in the plasma, also known as burning plasma.

While this state can help us unlock fusion energy, it also provides us glimpses of the conditions of the early universe. Subsequent experiments at the NIF provided us with more information about these conditions but also brought discrepancies in neutron spectrum data to the fore.

Supra thermal ions

Traditionally, the behavior of particles in fusion environments has been based on Maxwell distributions. However, researchers found that this approach overlooked critical kinetic effects arising in non-equilibrium scenarios and does not explain the presence of supra-thermal ions

To address this hurdle, a research team led by Jie Zhang at the Chinese Academy of Sciences proposed a novel model centered around large-angle collision dynamics, a revolutionary and multi-faceted approach.

Employing a hybrid-particle-in-cell simulation code called LAPINS, the team conducted high-precision simulations of ICF-burning plasma to gain insights into the fusion reaction. They found that large-angle collisions promote ignition reaction by 10 picoseconds, which could help improve fusion reactions.

The simulation detected the presence of supra-thermal D ions with energies below the threshold of 34 keV. This is important since the energy deposition is twice that of alpha particles. The team also found that alpha particle densities at the center of the hotspot were enhanced by 24 percent.