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martyb writes:

How 'Miniature Suns' Could Provide Cheap, Clean Energy:

Nuclear fusion has long been heralded as a potential answer to our prayers. But it's always been "thirty years away", according to the industry joke.

Now several start-ups are saying they can make fusion a commercial reality much sooner.

[...] A major challenge is how to build a structure strong enough to contain the plasma - the very high-temperature nuclear soup in which the fusion reactions take place - under the huge pressures required.

Exhaust systems will "have to withstand levels of heat and power akin to those experienced by a spaceship re-entering orbit," says Prof Ian Chapman, chief executive of the UK Atomic Energy Authority (UKAEA),

Robotic maintenance systems will also be needed, as well as systems for breeding, recovering and storing the fuel.

"UKAEA is looking into all these issues, and is building new research facilities at Culham Science Centre near Oxford to work with industry to develop solutions," says Prof Chapman.

[...] Oxfordshire-based Tokamak Energy is working on spherical tokamaks or reactors that use high temperature superconductors (HTS) to contain the plasma in a very strong magnetic field.

"High temperature" in the context of this branch of physics means a distinctly chilly -70C or below.

[...] The company has built three tokamaks so far, with the third, ST40, built from 30mm (1.2in) stainless steel and using HTS magnets. This June it achieved plasma temperatures of more than 15 million C - hotter than the core of the sun.

The firm hopes to be hitting 100 million C by next summer - a feat Chinese scientists claim to have achieved this month.

"We expect to have energy gain capability by 2022 and be supplying energy to the grid by 2030," says Mr Carling.

Meanwhile in the US, MIT [Massachusetts Institute of Technology] is working with the newly-formed Commonwealth Fusion Systems (CFS) to develop Sparc, a doughnut-shaped tokamak with magnetic fields holding the hot plasma in place.

Funded in part by Breakthrough Energy Ventures, a fund led by Bill Gates, Jeff Bezos, Michael Bloomberg and other billionaires, the team hopes to develop fusion reactors small enough to be built in factories and shipped for assembly on site.

[...] "With the new HTS magnet technology, a net-energy fusion device can be much, much smaller - Sparc would be about one sixty-fourth the volume and mass of Iter[*]," says Martin Greenwald, deputy director of MIT's plasma science and fusion centre.

[*] From Wikipedia, ITER: "(International Thermonuclear Experimental Reactor) is an international nuclear fusion research and engineering megaproject, which will be the world's largest magnetic confinement plasma physics experiment. It is an experimental tokamak nuclear fusion reactor that is being built next to the Cadarache facility in Saint-Paul-lès-Durance, in Provence, southern France."

And, tokamak: "(Russian: Токамáк) is a device that uses a powerful magnetic field to confine a hot plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being developed to produce controlled thermonuclear fusion power. As of 2016, it is the leading candidate for a practical fusion reactor."

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