At a Shanghai facility the size of a soccer field, Chinese scientists are firing powerful laser beam pulses at a tiny pair of gold cones in a bid to replicate the nuclear fusion process at the heart of the sun.
The cones, as small as pencil tips, have narrow ends which face each other and emit a plasma of hydrogen. When the two hot gas streams collide at precisely the right time and place, and in the right manner, they trigger a fusion reaction – the process which ultimately could provide a source of endless, sustainable energy.
With government funding of 1 billion yuan (US$156 million) over six years, Zhang Zhe and his colleagues from the Chinese Academy of Sciences’ Institute of Physics in Beijing began their unprecedented experiments at the Shenguang II laser facility in Shanghai last summer.
The research team has conducted three tests so far, with another scheduled for next month, and encountered some unexpected challenges. But initial results suggest the theory works and part of the findings were published recently in domestic peer-reviewed journal Acta Physica Sinica.
“Our goal is to achieve sustainable fusion,” Zhang said in a phone interview, “the cones can be mass-produced and loaded as bullets in a machine that will rotate and fire like a Gatling gun”.
The race to fusion power heated up in 2021, when researchers with the US National Ignition Facility (NIF) achieved an energy output eight times greater than ever before. While the output was still lower than the energy input, the breakthrough gave hope as well as added pressure to research teams in other countries, including China.
The NIF experiment aimed more than 100 extremely strong laser beams at a single target, using some of the largest laser generators on Earth, producing enough heat to deform mirrors but also reducing accuracy after repeated shots.
In China, researchers were looking for a cheaper, simpler way to achieve fusion with a less powerful laser. One result was the double-cone ignition scheme developed in 1997 by Zhang Jie, a leading Chinese physicist and former president of Shanghai Jiao Tong University.
The plasma generated by relatively weak laser beams on a single target was insufficient to create the right conditions for fusion, but when two plasma streams hit each other, the temperature, density and pressure of the gas would increase significantly to allow two atoms to fuse into one and release energy in the process.
The idea remained on paper for two decades because the required cutting-edge laser technology was not available. However, Chinese scientists have recently built some of the world’s most powerful ultra-fast laser sources able to release a considerable amount of energy in a split second. It was these new technologies which paved the way for the government’s greenlight of the experiment in Shanghai last year.
The gold cones vaporize after fusion, but “the cost of gold will be extremely small – if not negligible – in the future operation of a power plant”, Zhang Zhe said. “A small grain of gold can make thousands of cones.”