Recently a flood of articles appeared in the press showing a US satellite photo of what was described as a huge laser facility under construction in southwestern China. Readers were given the impression that this was a newly-discovered secret project. The reality is rather different.
The three big players in laser fusion today are the US, France and China. China already operates the world’s third most powerful laser, the Shenguang-III, located near the “Science City” Mianyang in Sichuan Province. (The Chinese expression shénɡuānɡ (神光) translates as “divine light.”) Completed in 2015, Shenguang-III is hailed in China as one of the country’s greatest technological accomplishments.
Before Shenguang-III went on line, planning had already begun for a much larger laser system, Shenguang-IV, capable of reaching fusion ignition. This is doubtless the facility shown in the satellite photo. While up-to-date information on Shenguang-IV is hard to come by, Chinese sources had already reported that the project was under construction in Mianyang and was to be completed “sometime after 2020.” It would have up to 228 laser beams and a total pulse energy of between 1.5 and 2 megajoules.
Shenguang-IV would thereby rival the largest presently existing system, the US National Ignition Facility (NIF), and most likely be superior to it in important respects. Shenguang-IV can take advantage of technologies that were not available when NIF was built.
Given that NIF is already a relatively old facility – construction began in 1997 and was completed in 2009, with no follow-on project – this would make China Number One in the world in terms of its capabilities for laser fusion.
One should not forget that Mianyang, where the Shenguang laser facilities are situated, is the leading center in China for research and development of nuclear weapons, directed energy weapons and other military-related advanced technologies. Nuclear weapons are produced there.
Among many other things, Mianyang is also the site of the hypersonic wind tunnel, JF-12, the most powerful in the world up to the inauguration of China’s JF-22 tunnel two years ago.
The Shenguang facilities belong to the legendary Chinese Academy of Engineering Physics (CAEP), formerly designated as the “Ninth Institute.” From its creation in 1958 it played a key role in China’s effort to develop nuclear weapons, in the context of the “two bombs, one satellite” (两弹一星) strategy.
Institute of Mechanics, Chinese Academy of Sciences
Apart from being one of the most important pathways to fusion as a practical energy source, laser fusion has always had a strong military connection. Bombarding a particle of fusion fuel the size of a grain of sand with a gigantic pulse of laser energy triggers the laboratory-scale equivalent of a tiny hydrogen bomb explosion. Among other things, this allows bomb-relevant physics to be investigated in detail without violating the Comprehensive Nuclear Test Ban Treaty, which both the US and China have signed.
At the same time one should not underestimate the importance of the Shenguang laser facilities for China’s ambition to become the first nation to build a functioning fusion power plant.
The main thrust of its fusion effort lies in the direction of magnetic confinement systems, particularly tokamaks – but China is not putting all its eggs into one basket. There are unique advantages from employing laser fusion – and so-called inertial confinement in general. The advantages include ultra-high power densities and application to spacecraft propulsion.
China is also pursuing other forms of inertial confinement fusion, which are closely related to laser fusion.
Most interesting is the Z-FFR fusion-fission hybrid reactor project of Peng Xianjue, a leading researcher at the above-mentioned China Academy of Engineering Physics. In place of a laser, this reactor uses the so-called Z-pinch, in which a giant pulse of electrical energy compresses and ignites the fusion fuel. In Peng’s reactor the neutrons, generated by fusion reactions, trigger fission reactions in a surrounding blanket of fissile material, thereby releasing large amounts of energy.
A great advantage of this hybrid scheme is that the fusion part can operate below the breakeven, which is much easier to achieve, while the fission part operates below the level of criticality, making a run-way chain reaction impossible.
The key step to its realization – the construction of the world’s most power Z-pinch device — was approved by the government in 2021 for construction in Sichuan province’s Comprehensive Science Center at Xinglong Lake. According to some reports, construction in already under way.
Meanwhile it is interesting to speculate about the timing of the recent press revelations about a mysterious new laser facility in Mianyang. We can be sure that the US takes dozens, if not hundreds, of satellite reconnaissance photos of the Mianyang region every year. The construction of such a huge laser facility would hardly have escaped attention.
