For the first time, Chinese scientists have moved thermonuclear plasma beyond the density limit, which is considered the "middle" of tokamak fusion reactors for decades.
This achievement was achieved on the EAST (Experimental Advanced Superconducting Tokamak) tokamak furnace, commonly known as China's "artificial sun", and is considered an important step on the path towards the goal of igniting thermal nuclei.
The research results were published on January 1st in the journal Science Advances, co-led by a scientific team led by Professor Ping Zhu (Hua Zhong University of Science and Technology) and Associate Professor Ning Yan (Hufei Institute of Physics, Academy of Science of China).
The group first experimentally tested a special plasma state, called "unlimited density mode", in which plasma remains stable even when density increases very high.
In thermonuclear reactions - a process of generating energy similar to in the Sun - deuterine and tritium fuels must be heated to about 150 million degrees Celsius. At this temperature, the heat nucleus power generated increases very rapidly as plasma density increases. Therefore, in theory, the higher the density, the greater the power generation potential.
However, in reality, tokamak kilns have long been limited by a certain density threshold. When this threshold is exceeded, plasma often becomes unstable, disrupting the holding process and forcing experiments to stop. This is one of the biggest physical barriers hindering the improvement of thermal productivity.
The research team at EAST has demonstrated that this limit is not immutable. By developing a completely new high-density plasma operation method, they show that it is possible to push plasma density far beyond previous empirical limits without causing destructive instability.
This breakthrough is based on a relatively new theoretical framework called "plasma-wall self organization" (PWSO), proposed by French scientists. According to this theory, the density limit not only depends on the plasma itself, but is also closely linked to how plasma interacts with the metal wall of the reactor.
When the interaction between plasma and the furnace wall reaches a suitable equilibrium state, a new operating mode may appear, in which physical bombardment processes from the furnace wall help stabilize plasma instead of causing instability as before.
According to Professor Ping Zhu, this discovery opens up "a practical and expandable path" to extend the density limit in tokamak, including new generation thermonuclear devices.
This is especially important for the ignition target - a time when the thermonuclear reaction can maintain itself without needing external energy supply.
In the context of the increasingly fierce global race for clean energy, new results from China's "artificial sun" show that a major barrier of thermonuclides is gradually being removed, bringing the prospect of near-infinite energy sources a clearer step forward.
