Inside our Sun, hydrogen is constantly being converted into helium, producing a tremendous amount of energy – enough to heat the planets, melt comets, and support life on Earth. So it’d be pretty good if we could replicate that process on our own planet, right?
That’s what scientists have been trying to do for decades now. Nuclear fusion, also known as “star in a jar” technology, has seemingly always been on the horizon but never quite within reach. A number of recent breakthroughs, however, suggest we may soon be mimicking the power of the Sun on Earth.
One of the most recent breakthroughs was made using Germany’s Wendelstein 7-X (W7-X) fusion device. In early December 2016, scientists at the Max Planck Institute in Greifswald managed to sustain a hydrogen plasma in the experimental reactor for a few milliseconds.
It may not sound like a big deal, but this was hugely significant for a number of reasons. First, to kickstart nuclear fusion, extremely high temperatures – about 100 million °C (180 million °F) – are required to make a plasma cloud. This cloud must also be confined by extremely powerful magnets so that it does not touch the cold walls of the reactor.
Second, this process had only previously been achieved with a helium plasma. Hydrogen fusion provides much more energy, so is much more desirable. Just getting to this stage at all at the W7-X has taken 19 years and cost $1.1 billion.
The W-7X is a type of fusion reactor known as a stellarator, which is shaped like a twisted donut to keep the plasma confined, by twisting the magnetic fields around it. Another type of fusion reactor, known as a tokamak, achieves this twisted magnetic field in a different way. They are more regularly shaped donuts, but use a large current to achieve the same twisting effect in the plasma. Both methods have their advantages and disadvantages.
In a bit of a coincidence, last December also saw a tokamak reach a major breakthrough. Scientists at the National Fusion Research Institute (NFRI) in South Korea managed to sustain a high-performance plasma for a mammoth 70 seconds, a new world record. It was widely reported that this was done with a hydrogen plasma.
This might beg the question, why even bother with the stellarator if the tokamak is so much more impressive? The reason is that while the stellarator is more complex, it is easier to maintain, and if it can be improved then it could rival the tokamak in sustaining a plasma.
It’s unclear who is going to win the race to make a working “star in a jar”. Another project underway is the International Thermonuclear Experimental Reactor (ITER) in France. This international project is going down the tokamak route, but has had a troubled development time; it was first initiated way back in 1988.
However, they are hopeful of generating their first plasma by 2025. If it all works, this reactor – and the others – will be a precursor of what is to come.
And, well, that could be rather fantastic. Nuclear fusion has the added benefit of generating zero waste products, and a working reactor would theoretically produce more energy than is put in. This would give us an essentially limitless and clean source of energy.
Whether the dream will be realized remains to be seen. But, for nuclear fusion at least, we've had a rather good year. A working “star in a jar” may not be too far away.