The discovery of ten previously unknown plasma phases could bring us closer to fusion power.

 

The discovery of ten previously unknown topological phases of plasma has been made possible by a new method of classifying magnetised plasma.

Learning more about these phases, particularly the transitions between them, could aid plasma physicists in their quest for the energy's "white whale," plasma fusion. Because the transitions between them enable edge modes, or waves at the plasma surfaces' intersections, this is the case.

These unusual excitations could expand the range of applications for magnetised plasma.

"These findings may lead to applications of these exotic excitations in space and laboratory plasmas," said Princeton Plasma Physics Laboratory researcher Yichen Fu (PPPL).

"The next stage will be to figure out what these excitations can do and how they can be used."

Recent research has begun to look at plasma topologically, that is, the shapes of the waves that exist within it.

The topological phases of cold magnetised plasma, as well as the transitions between them, have not yet been thoroughly investigated. This is significant because it can aid our understanding of how plasma interacts with matter.

Diagram of the topological phases. (Fu & Qin, Nature Communications, 2021)

Fu and his colleague, PPPL physicist Hong Qin, sought to mathematically describe the topological phases of a cold plasma in a uniform magnetic field. They found 10 different novel phases, separated by edge modes - the boundary between two topologically different regions within the plasma. Numerical studies verified the pair's findings.

"The discovery of the 10 phases in plasma marks a primary development in plasma physics," Qin said.

"The first and foremost step in any scientific endeavor is to classify the objects under investigation. Any new classification scheme will lead to improvement in our theoretical understanding and subsequent advances in technology."

What those advances might be is not speculated in the paper, but there are some interesting possibilities. Plasma is often called the fourth state of matter, a gas in which electrons have been stripped from the atoms therein, forming an ionized material.

It's abundant in space - in fact, it's the state of matter found in stars, which is key to a potential plasma technology.

Deep in their plasma cores, stars fuse nuclei to form heavier elements, a process that generates vast amounts of energy. Scientists have been working towards plasma fusion here on Earth as a form of energy production that will be clean and practically limitless.

As you might imagine, this is extremely difficult. We need to be able to maintain a stable plasma at temperatures hotter than the Sun for long enough to generate and extract energy. There are many obstacles, and so we're pretty far from that goal - but better understanding plasma can only bring us closer.

This research represents a step in that direction.

"The most important progress in the paper is looking at plasma based on its topological properties and identifying its topological phases," Fu said.

"Based on these phases we identify the necessary and sufficient condition[s] for the excitations of these localized waves. As for how this progress can be applied to facilitate fusion energy research, we have to find out."

The research has been published in Nature Communications.