One-of-a-kind fusion experiment comes online
A team of university engineers managed an improbable scientific coup this summer, completing a new fusion research device with surplus property, ingenuity and a small army of Wisconsin companies.
At exactly 5:15 p.m. on Tuesday, Aug. 31, a rousing cheer echoed through the HSX Plasma Laboratory in Engineering Hall. The occasion was the “first plasma” for this 20-ton machine, a glowing ring of light that told them a mathematical theory and years of hard labor had delivered.
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“The key to making this happen was working cleverly and cheaply. Our motto was, ‘We can turn junk into gold.'”
David Anderson Bottom: Team leaders from left are professor David Anderson and electrical engineering researchers Simon Anderson and Joe Talmadge. Photo: Jeff Miller |
Plasmas are achieved by heating matter to intensely high temperatures, creating a glowing, gas-like state that can conduct electricity. Plasmas on earth include neon signs, lightning bolts and the Northern Lights, and they’re the building blocks for fusion energy – a potentially boundless energy source. “Making a first plasma is a momentous occasion,” says associate scientist Joseph Talmadge, a co-investigator in HSX, who admits that the elation is combined with “tremendous relief.”
“Eight years of hard work was on the line,” adds David Anderson, the principal investigator in the project.
The 14-member team has good reason to celebrate. HSX (or the Helically Symmetric Experiment) is an entirely new type of stellarator fusion experiment that combines the best attributes of two existing technologies.
“It’s never been done like this before, an entirely paperless design,” Anderson says. HSX has been designed from the inside-out, by first determining the physics properties through computer models, then designing the machine to achieve the perfect magnetic field.
The shape of HSX is certainly its signature and the key to its unique properties. The vacuum chamber looks like a warped donut, with a series of helical twists and turns girdled by thick coils of copper magnets. The device will confine plasmas in a magnetic field, while generating temperatures of up 10 million degrees.
Although it may be decades from application, fusion holds tremendous promise as an alternative energy source. The same way the sun creates energy, fusion is achieved by melding atomic nuclei of two elements under extremely high temperatures, which releases energy.
Fusion fuel is essentially sea water, and one gallon burned in a fusion reactor would produce the equivalent energy of burning 300 gallons of gasoline. HSX combines elements of two existing styles of plasma containment experiments known as tokamaks and stellarators. Tokamaks have achieved the best results to date, but they also require a strong current in the plasma itself. Stellarators don’t need that current, making them potentially more attractive as power reactors.
But they don’t produce the high-quality magnetic field that confines plasmas to reach reach higher temperatues. HSX solves that problem by achieving symmetry in the magnetic field through its oddly shaped and complex magnet coils. The plasma-confining energy is located in coils outside of the plasma itself, making it a more stable and attractive as a reactor.
That HSX was ever completed is somewhat miraculous, given the era in which it started. The Department of Energy scaled back fusion research in the 1990s, and had especially targeted alternative technologies to the tokamak. The project survived because of the strong advocacy of one DOE official. Today, alternative fusion is in favor again, mainly because of the success of smaller-scale experimental projects like HSX and the robust scientific results they are producing.
UW–Madison is a hotbed for alternative fusion and home to two other projects – the Pegasus spherical torus and the Madison Symmetric Torus. DOE support for the HSX project has totaled $7.5 million since 1993, modest by fusion research. Anderson says that the crew had to adopt a hand-me-down mentality, accepting cast-offs from the better-endowed physics labs to build this world-class facility for the available dollars.
“The key to making this happen was working cleverly and cheaply,” he says. “Our motto was, ‘We can turn junk into gold.'”
In fact, most of the power supplies for HSX are recycled goods. They picked up 20 old motor generators, each with 1.5-ton flywheels the size of tractor tires, from the scrap heap of Los Alamos National Laboratory in New Mexico. And they scooped up a high-powered gyrotron, which produces intense microwave energy, from Oak Ridge National Laboratory and its 1.6 megawatt power supply from Lawrence Livermore Labs in California.
HSX is a major Wisconsin success story, with more than 40 companies providing unprecedented support in building the device. They provided the welding, precision machining and quality materials, and showed great creativity in fabricating this one-of-a-kind machine. For example, the vacuum chamber was fabricated with the use of explosives that act as a hammer to precisely form the stainless steel against precision machined molds.
Anderson laughingly recalls when one of their finished pieces was stolen from a rural storage shed. They began calling scrap dealers around the area, and found one who reported purchasing “a piece of culvert that was run over by a truck.” Bingo.
The thief, who was caught, sold it for $15 to the scrap dealer, and reportedly spent his windfall on cigarettes and a tank of gas, not realizing the strange chunk of metal had $20,000 of work behind it.
HSX is still in its infancy. “The first plasma really marks the line between the construction and the research phase,” says Talmadge.
Collectively, the research will inch its way toward the big question: Is this the road to making fusion energy a reality?
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