Long Read - Outside Insights: Alternative Fusion

Welcome back to our "long read" series. This time, it's an "Outside Insight" into different fusion technologies. "Although ITER is the biggest, it’s not the only game in town." Read on to get an overview of all the 'kids' on the block!

Article authored by Science Journalist Daniel Clery, author of 'A Piece of the Sun: The Quest for Fusion Energy,' for the September 2019 issue of 'Fusion In Europe'

ITER is the biggest game in town when it comes to fusion, the culmination of seven decades of research by many thousands of scientists consuming billions in funding. The scale of ITER makes sense: tokamaks have, since the 1960s, shown the greatest promise of being able to produce a sustainable fusion reaction, and most indicators suggest that the bigger you build a tokamak, the better it performs. That’s how we’ve ended up with a machine 30 metres across and nearly as many tall. And at €20 billion-plus, ITER is so expensive that governments representing more than half the world’s population have joined forces to share the cost.

Alternatives to ITER

Although ITER is the biggest, it’s not the only game in town. Other approaches have kept going at much lower levels of funding as an insurance policy, if you will, in case tokamaks hit a roadblock on the way to energy production. These include stellarators, which hold plasma in a vessel shaped like a demented doughnut using crazily contorted magnets. The Wendelstein 7­X reactor in Germany is the latest example of this technology. Then there is inertial confinement fusion, which aims to crush a tiny capsule of fuel to burning point with a burst of energy, such as that supplied by the giant lasers of the National Ignition Facility in California.

But ever since the early days there’s been a third stream in fusion research beyond these publicly funded projects. These are typically driven by an inspired individual who has come up with a new fusion scheme that will provide a shortcut to energy production, thereby saving the planet – and making a tidy profit for them and their backers. Historically, most of these efforts have ended when they simply ran out of money – fusion is an expensive business. But that hasn’t stopped other budding fusioneers having a shot themselves.

Golden age of privately funded fusion

Today we’re in something of a golden age of privately funded fusion. Barely a year goes by without another startup announcing its ambitious plans. Some of these companies have raised hundreds of millions of dollars from internet billionaires and other wealthy philanthropists, venture capital firms, sovereign wealth funds, and anyone else willing to take a gamble on revolutionising the energy industry. Some efforts are based on entirely new fusion schemes, others on old ideas given new life by updated technology and materials. They all have a long way to go to catch up with tokamaks but perhaps one of them will get lucky, so long as their bank account holds out.

First fusion entrepreneurs

Perhaps the first fusion entrepreneurs were US physicist Keith Brueckner and business-man Kip Siegel. In the 1960s, Brueckner independently came up with a scheme for using lasers and Siegel sunk $20 million into building him a lab and supporting his research. For a spell, in the early 1970s, they were competing neck-and-neck with inertial fusion researchers at US national laboratories. But as problems mounted, Brueckner returned to academia in 1974 and Siegel, while speaking to a Congressional committee in 1975 to request research funding, suffered a stroke that proved fatal.

An unlikely backer

The most unlikely backer of fusion research was Bob Guccione, the publisher of Penthouse magazine. In 1980 he began supporting fusion scientist Robert Bussard, after reading an interview in his own magazine Omni. Bussard believed he could make tokamaks smaller and more cheaply by using very powerful magnets to hold the plasma in place. Bussard spent $17 million of Guccione’s money setting up a company that grew to a staff of 85. But when no other backers came forward and a share issue flopped, Guccione pulled the plug.

Tokamak: an enduring idea

The idea of a high­field tokamak did not die, however. The Massachusetts Institute of Technology pursued this concept with its series of Alcator reactors (Alcator is short for Alto Campo Toro, or “high field torus”). The last reactor, Alcator C-Mod, was closed in 2016 but MIT spun out the company Commonwealth Fusion Systems in 2018 to continue the work and it has raised more than $100 million to develop a compact tokamak called SPARC. The company is hoping that a new formulation of high-temperature superconductor – a tape incorporating a layer of superconducting yttrium barium copper oxide – will allow it to make magnets that are small, powerful, and cheap to run.

The Massachusetts team will be running to catch up with a small company set up a decade ago near Oxford, UK, to develop compact fusion reactors. Tokamak Energy is also betting on magnets made from high-temperature superconducting tapes. They plan to use them to build a spherical tokamak, a variation on the conventional design that is plumped up so that it looks more like a cored apple than a doughnut. The idea is that plasma is held more stably when it is close to the central hole of the torus and the spherical shape and narrow hole maximises the time plasma spends close to it. The company has built a 2-metre wide spherical tokamak using conventional magnets that achieved a temperature of 15 million degrees in 2018 and is working towards 100 million degrees, the sort of temperature at which fusion happens.

Field­ reversed configuration

Other fusion startups are straying further from the mainstream. Several companies are banking on a phenomenon called a field­ reversed configuration, or FRC. They make these using a plasma gun that shoots out a blob of plasma shaped like a rotating smoke ring. The charged particles in the spinning plasma generate a magnetic field and this exerts a force which holds the plasma ring together. Discovered in the 1950s, early FRCs only lasted a few millionths of a second. But fusion startups are now using them to contain plasma long enough to be heated to fusion temperatures.

Tri Alpha Energy in California is trying to extend the lifetimes of FRCs. They’ve built a series of devices culminating in “Norman” – named after the company’s founder, the physicist Norman Rostoker who died in 2014. Norman has a 25-metre long vacuum tube with a plasma gun at both ends. These simultaneously fire FRCs towards the centre at a million kilometres per hour where they collide and merge, creating a super-hot, cigar shaped FRC about as long as a small car. Beams of neutral particles are then fired into the FRC to stabilise and heat it. Norman can now make FRCs that last 10,000 times longer than in the early days and heat them to tens of millions of degrees.

General Fusion in Canada also uses FRCs but in a very different way. Founded by Michel Laberge, who quit designing laser printers in 2001 to do something more worthwhile, the company has built a plasma gun that fires an FRC into a spherical reaction chamber. At the same time, a large number of pneumatic pistons – as many as 400 and each the size of a torpedo – slams down in unison onto the outer surface of the reaction chamber. This creates a converging shock wave that arrives at the centre of the chamber just as the FRC does, crushing and heating it enough to spark fusion. The company is working on the different components and plans to put them together into a demonstration plant sometime in the next few years.

More exotic schemes

Other schemes are even more exotic. EMC2 of California has been working for decades on a device called a Polywell, another brainchild of the late Robert Bussard. The Polywell uses an arrangement of ring-shaped electromagnets to trap electrons in the centre of the device. Once there are enough electrons held there, the electric charge will exert an attractive force on positive ions around the edge of the device and accelerate them towards the centre where, with luck, many will collide and fuse. Another fusion maverick is Eric Lerner whose company, Lawrenceville Plasma Physics in New Jersey, is developing a device called a dense plasma focus. This uses intense pulses of electric field to create filaments of plasma in a gas. These filaments twist themselves into a tight ball called a plasmoid. Magnetic fields in the plasmoid accelerate electrons to high speed which, in turn, heats the plasmoid to extreme temperatures. Plasmoids only last 10 billionths of a second but Lerner says the process can heat them to three billion degrees.

Fusion performance

This is only a taster of the menagerie of fusion startups that are out there. Although some are making huge progress, tokamaks remain way out in front in terms of fusion performance. Nevertheless, the new kids on the block continue to make bold predictions of how soon they will have viable power-producing prototypes – always a lot sooner than ITER. So, will the power plant of the future be a giant plasma-filled doughnut, a smaller apple-shaped cousin, or something like Norman, Poly-well, or plasmoids? It’s time to lay your bets.