January 21, 2022 5:02 pm

China lights up its ‘artificial sun’ for record time of 17 minutes




Many countries are experimenting with future fusion reactors, which promise clean and unlimited energy from the stars. One of the nations that is making a greater effort in recent years is China. If just six months ago you announced that your reactor tokamak superconductor avanzado experimental (EAST) had been able to maintain a plasma temperature of 120 million degrees Celsius for 101 seconds, now the same team has accomplished another feat: holding the plasma for 1,056 seconds (17 minutes). Of course, at a lower temperature: 70 million degrees Celsius.

‘We achieved a plasma temperature of 120 million degrees Celsius for 101 seconds in an experiment in the first half of 2021.

This time, the steady-state plasma operation held for 1,056 seconds at a temperature close to 70 million degrees Celsius, which has left a solid scientific and experimental basis to better understand the operation of fusion reactors, “he said in a statement Gong Xianzu, a researcher at the Institute of Plasma Physics of the Chinese Academy of Sciences (ASIPP), who is in charge of the experiment carried out in Hefei, capital of Anhui province in eastern China.

The goal is to emulate the power of the stars and create huge amounts of energy by injecting a small amount of gas deuterium Y tritium (hydrogen), which is heated to high temperatures and becomes a ionized plasma. However, in order for a chain fusion reaction that plasma has to be heated up to 150 million degrees Celsius, more than double that of the Chinese reactor.

A success, but not a milestone

Because the reactors will be functional when they manage to keep the plasma at those temperatures for a long time. “This is a serious experiment, the biggest Chinese machine. But it is not the one that achieves the best parameters in terms of fusion gain; that is, in energy obtained compared to that used in the reaction “, he explains to ABC Joaquin Sanchez, director of the National Fusion Laboratory, dependent on Ciemat. “They have specialized in long pulses, which is technologically interesting, but to a lesser degree from a physics point of view.”

In fact, there are no scientific publications yet (not even in prepress format) explaining the specific experiment, so there are some gaps in how this success has been achieved. «With the existing public information, it is not known if the temperature of the electrons has been increased, which is the most probable; or that of ions, which is more difficult to rise when long pulses fed by radiofrequency are made, ”says Sánchez. «There has been progress in stretching the pulse, but it is not a ‘historic’ breakthrough».

Differences with the ITER project

The Chinese prototype is the first model tokamak with a non-circular cross section, although the Asian giant has other similar experiments, such as the HL2M and the HL2A, whose difference is that they are not superconducting and are smaller. The EAST would be the most similar machine to the ITER project, (International Thermonuclear Experimental Reactor), a large-scale scientific experiment aimed at proving that fusion reactors are viable. This prototype, created by an alliance between the European Union, Japan, the United States, South Korea, India, Russia and China itself, will use ultra-high-energy neutrons, produced by fusion, that escape the magnetic field and hit the walls. metallic elements from the tokamak chamber, transmitting their energy to the walls in the form of heat. Some neutrons react with lithium on metal walls, creating more tritium fuel for fusion and chain reaction. The water that circulates through the walls of the tokamak receives the heat and turns into steam. In a commercial reactor, this steam will drive turbines to produce electricity.

It is planned that The first tests begin at the Cadarache facilities (France) from 2026, although the infrastructure is still under construction. However, when the experiments begin, they will be much more ambitious than those in China alone: ​​in the first tests the aim is to reach the 500 seconds of work at high power (just over 8 minutes) and the 1,500 at half power (25 minutes), in both cases with temperatures above 100 million degrees. “If we compare it with EAST, it is another dimension,” says Sánchez.

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