To achieve fusion gain—more energy out than heating pumped in—researchers will have to make FRCs last for at least a second. Although that feat seems a long way off, Santarius says Tri Alpha has shown a way forward. “If they scale up size, energy confinement should go up,” he says. Tri Alpha researchers are already working with an upgraded device, which has differently oriented ion beams and more beam power. TAE Chief Experimental Strategist Pr. Houyang Guo revealed during a plasma physics seminar held at the University of Wisconsin–Madison College of Engineering on April 29, 2013 that C-3 will be increased in size and heating power, in order to achieve 100 milliseconds to 1 second confinement times. He also confirmed the company has a staff of 150 people
Tri Alpha team has revealed how fast ions, edge biasing, and other improvements have enabled them to produce FRCs (Field Reverse Configuration plasmas) lasting 5 milliseconds, a more than 10-fold improvement in lifetime, and reduced heat loss. “They’re employing all known techniques on a big, good-quality plasma,” Wurden says. “It shows what you can do with several hundred million dollars.”
In 2015, Daniel Clery reports that Tri Alpha researchers are already working with an upgraded device, which has differently oriented ion beams and more beam power.
Developing a stable plasma state with high-beta (ratio of plasma to magnetic pressures) is of critical importance for an economic magnetic fusion reactor. At the forefront of this endeavour is the field-reversed configuration. Here we demonstrate the kinetic stabilizing effect of fast ions on a disruptive magneto-hydrodynamic instability, known as a tilt mode, which poses a central obstacle to further field-reversed configuration development, by energetic beam injection. This technique, combined with the synergistic effect of active plasma boundary control, enables a fully stable ultra-high-beta (approaching 100%) plasma with a long lifetime.
Conventional field-reversed configurations (FRCs), high-beta, prolate compact toroids embedded in poloidal magnetic fields, face notable stability and confinement concerns. These can be ameliorated by various control techniques, such as introducing a significant fast ion population. Indeed, adding neutral beam injection into the FRC over the past half-decade has contributed to striking improvements in confinement and stability. Further, the addition of electrically biased plasma guns at the ends, magnetic end plugs, and advanced surface conditioning led to dramatic reductions in turbulence-driven losses and greatly improved stability. Together, these enabled the build-up of a well-confined and dominant fast-ion population. Under such conditions, highly reproducible, macroscopically stable hot FRCs (with total plasma temperature of ∼1 keV) with record lifetimes were achieved. These accomplishments point to the prospect of advanced, beam-driven FRCs as an intriguing path toward fusion reactors. This paper reviews key results and presents context for further interpretation.
Researchers had theorized that an FRC could be made to live longer by firing high-speed ions into the plasma. Michl Binderbauer, Tri Alpha’s chief technology officer, says that once the ions are inside the FRC, its magnetic field curves them into wide orbits that both stiffen the plasma against instability and suppress the turbulence that allows heat to escape. “Adding fast ions does good things for you,” says Glen Wurden of the Plasma Physics Group at Los Alamos National Laboratory in New Mexico. Tri Alpha collaborated with Russia’s Budker Institute of Nuclear Physics in Akademgorodok, which provided beam sources to test this approach. But they soon learned that “[ion] beams alone don’t do the trick. Conditions in the FRC need to be right,” Binderbauer says, or the beams can pass straight through. So Tri Alpha developed a technique called “edge biasing”: controlling the conditions around the FRC using electrodes at the very ends of the reactor tube.
Tri Alpha itself has raised over $150 million from the likes of Microsoft co-founder Paul Allen and the Russian government’s venture-capital firm, Rusnano.
Tri-alpha Energy has started to let its employees publish results and present at conferences. With its current test machine, a 10-metre device called the C-2, Tri Alpha has shown that the colliding plasmoids merge as expected, and that the fireball can sustain itself for up to 4 milliseconds — impressively long by plasma-physics standards — as long as fuel beams are being injected. Last year, Tri Alpha researcher Houyang Guo announced at a plasma conference in Fort Worth, Texas, that the burn duration had increased to 5 milliseconds. The company is now looking for cash to build a larger machine.
As a science programme, it’s been highly successful,” says Hoffman, who reviewed the work for Allen when the billionaire was deciding whether to invest. “But it’s not p–11B.” So far, he says, Tri Alpha has run its C-2 only with deuterium, and it is a long way from achieving the extreme plasma conditions needed to burn its ultimate fuel.
Nor has Tri Alpha demonstrated direct conversion of α-particles to electricity. “I haven’t seen any schemes that would actually work in practice,” says Martin Greenwald, an MIT physicist and former chair of the energy department’s fusion-energy advisory committee. Indeed, Tri Alpha is planning that its first-generation power reactor would use a more conventional steam-turbine system.
Solo notes from May 1, 2013.
-150 on staff
-5ms plasma lifetime, presently limited not by instabilities but by ~1ms confinement time (energy, particles)
-very reproducible discharges despite dynamic merging procedure
-Te ~100eV, Ti ~ 400eV
-20keV beam ions orbit passes through edge, important to keep neutral density down
-plasma guns help stabilize MHD instabilities, other turbulence by biasing & driving anti-rotation
– confinement scales like (Te * r_s)^2 which is very favorable
– planning C-3 device with 100ms-1s confinement times by increased size, heating power