Tri Alpha Energy, nuclear fusion startup, has raised $500 million. Tri Alpha’s setup borrows some of the principles of high-energy particle accelerators, such as the Large Hadron Collider, to fire beams of plasma into a central vessel where the fusion reaction takes place. Last August the company said it had succeeded in keeping a high-energy plasma stable in the vessel for five milliseconds—an infinitesimal instant of time, but enough to show that it could be done indefinitely. Since then that time has been upped to 11.5 milliseconds.
The next challenge is to make the plasma hot enough for the fusion reaction to generate more energy than is needed to run it. How hot? Something like 3 billion °C, or 200 times the temperature of the sun’s core. No metal on Earth could withstand such a temperature. But because the roiling ball of gas is confined by a powerful electromagnetic field, it doesn’t touch the interior of the machine.
The photos seen here were taken a few days before Tri Alpha began dismantling the machine to build a much larger and more powerful version that will fully demonstrate the concept. That could lead to a prototype reactor sometime in the 2020s.
Compact Toroidal injector test stand
The C2U is the world’s largest compact toroid device. 20 meters in length and 1.4 meters in diameter. Magnetic fields of 3.5 tesla deliver 1 megajoule in microseconds forming and accelerating compact toroids to 600,000 kilometers per hour.
Tri Alpha’s machine produces a doughnut of plasma, but in it the flow of particles in the plasma produces all of the magnetic field holding the plasma together. This approach, known as a field-reversed configuration (FRC), has been known since the 1960s. But despite decades of work, researchers could get the blobs of plasma to last only about 0.3 milliseconds before they broke up or melted away. In 1997, the Canadian-born physicist Norman Rostoker of the University of California, Irvine, and colleagues proposed a new approach. The following year, they set up Tri Alpha, now based in an unremarkable—and unlabeled—industrial unit here. Building up from tabletop devices, by last year the company was employing 150 people and was working with C-2, a 23-meter-long tube ringed by magnets and bristling with control devices, diagnostic instruments, and particle beam generators. The machine forms two smoke rings of plasma, one near each end, by a proprietary process and fires them toward the middle at nearly a million kilometers per hour. At the center they merge into a bigger FRC, transforming their kinetic energy into heat.
Previous attempts to create long-lasting FRCs were plagued by the twin demons that torment all fusion reactor designers. The first is turbulence in the plasma that allows hot particles to reach the edge and so lets heat escape. Second is instability: the fact that hot plasma doesn’t like being confined and so wriggles and bulges in attempts to get free, eventually breaking up altogether. Rostoker, a theorist who had worked in many branches of physics including particle physics, believed the solution lay in firing high-speed particles tangentially into the edge of the plasma. The fast-moving incomers would follow much wider orbits in the plasma’s magnetic field than native particles do; those wide orbits would act as a protective shell, stiffening the plasma against both heat-leaking turbulence and instability.
SOURCES – Technology Review, Physics of Plasmas, Trialpha Energy, Youtube, Science