June 27,China's two self-developed nuclear fusion reactor superconducting magnets have completed technical acceptance and full operating condition parameter testing. They are the world's largest fusion reactor toroidal field superconducting magnet and the compact fusion device high-temperature superconducting center solenoid coil.This move marks that the most difficult key components in the "artificial sun" engineering chain have been successfully completed, and the magnets that have been tested this time are 100% localized from raw materials and structural materials to equipment and processes.
Among them, the high-temperature superconducting central solenoid coil is the core component of the Compact Fusion Energy Experiment Device (BEST). Its main function is to induce and drive plasma current and dynamically adjust the plasma confinement shape. The rated operating current of the coil is 46.5 kA, and the maximum operating magnetic field of the 6 groups of coils reaches 19 Tesla.
According to a team from the Institute of Plasma Physics, Chinese Academy of Sciences, the higher the magnetic field, the more high-temperature plasma that can be confined in a limited space. Without this coil, the fusion reactor "cannot ignite."
The BEST device is planned to be completed by the end of 2027 and will demonstrate the first kilowatt-hour of electricity using nuclear fusion around 2030.
Scientists have already verified the principle of controllable nuclear fusion, but the real problem lies at the engineering level. To create an artificial sun, the fuel needs to be heated to hundreds of millions of degrees Celsius. No material can withstand such high temperatures for a long time. For decades, scientists have mainly relied on strong magnetic constraints to "hold up" the plasma so that the fireball does not hit the wall or extinguish.
The high-temperature superconducting strip that was tested this time has a real functional superconducting layer only one micron thick. It has to be processed and bent, stuffed into a steel pipe and then extruded. It seems to only change the shape, but it actually undergoes stretching, compression, and twisting at the same time. Loss of control in any process will cause the material to fail.
Team leader Qin Jinggang said that when he received the task six years ago, he only had two requirements: improve performance and lower price. At that time, it was still unknown how the design would be determined and where the materials would come from.After six years of research, not only has the performance been improved and stabilized, but all source equipment has also been domestically produced.
The same superconducting material once cost 400 yuan per meter, but now it has dropped to 100 yuan.More importantly, the weight, size and energy storage of this coil far exceed previous specifications. A single coil has increased from 350 tons to 580 tons, which means that the energy scale of future devices will also be larger.
Qin Jinggang admitted that passing the test this time only counts as 80%, and the remaining 20% still needs to be installed on the device, and its service stability and lifespan are assessed in harsh environments. Only by passing the test can the road to high-temperature superconducting be truly completed.
In recent years, China's "artificial sun" has been accelerating the refresh schedule. In January last year, the fully superconducting tokamak experimental device Eastern Super Ring (EAST) achieved steady-state operation of 100 million degrees Celsius plasma for 1,066 seconds, once again setting a new world record.
According to the mainstream path, controllable nuclear fusion uses deuterium extracted from seawater as fuel. The fusion energy of one liter of seawater is equivalent to 300 liters of gasoline. It produces almost no highly radioactive nuclear waste and no carbon emissions. There are about 45 trillion tons of deuterium in the earth's oceans, which can last for billions of years at the current rate of human energy consumption, which is equivalent to inexhaustible energy.