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David Anderson
November 16, 2017

Wisconsin’s fusion energy research at a crossroads

Written By: Will Cushman

David Anderson wants to help bring the energy source of the sun and stars home to Earth.

“Nuclear fusion is the holy grail of energy research,” says Anderson, the Jim and Anne Sorden Professor in electrical and computer engineering.

But replicating the process that takes place at the core of our sun—where enormous amounts of energy lead hydrogen nuclei to fuse into helium—is a tremendous challenge.

“But the payback is huge,” Anderson says.

Indeed, within the realm of existing and potential energy sources, nuclear fusion is unique. If the technology were to become commercially viable, it would likely have profound impacts on the world economy and geopolitics. That’s because unlike fossil fuels, nuclear fusion’s fuel—isotopes of hydrogen: deuterium from seawater and tritium from lithium, is nearly limitless. And fusion doesn’t produce greenhouse gasses. Renewables like wind and solar, while greatly improving, have problems with intermittency and large energy storage requirements.

Meanwhile, nuclear fission, the energy source of today’s nuclear power plants, is well-known for the radioactive waste it produces. Fusion energy would produce orders of magnitude less and more manageable radioactive waste, Anderson says.

For these reasons and others, the National Academy of Engineering has identified the development of nuclear fusion as an energy source as one of its “grand challenges” to solve in the 21st century. And some of the foundational research that could one day lead to that solution has been ongoing down the hall from Anderson’s first-floor office in Engineering Hall for some 16 years. That’s where his Helically Symmetric eXperiment, or HSX, whirrs away.

Fusion energy research can be divided into two broad categories that revolve around devices whose names sound straight out of Star Trek: tokamaks and stellarators. Both machines use powerful magnetic fields to contain very high-temperature thermonuclear plasmas. The HSX is a stellarator; one of a handful around the world and the only device with its special kind of magnetic field structure. International collaborations are common in the research field, Anderson says, including his collaborations with German and Japanese researchers.

A 30-ton bulbous mass of metal and magnets the size of a garage, the HSX might look to someone who doesn’t understand it like an abstract expressionist sculpture. But the vaguely donut-shaped device is no random concoction: The undulating magnets that coil around it are precisely engineered to within a couple millimeters. This coil creates a powerful magnetic field that contains plasma within the vacuum inside. Research by Anderson and his colleagues since the HSX first came online in 2001 has centered on experimentally verifying the predicted improvements in plasma confinement expected from the weird shaping.

For years, tokamaks were considered by many researchers to be more promising devices for nuclear fusion energy production, and there are many more tokamaks around the world than stellarators. But tokamaks have stability issues that appear increasingly insurmountable, Anderson says, and a 2015 article in Science magazine titled, “The bizarre reactor that might save nuclear fusion,” describes stellarators like the HSX as the best hope for fusion energy dreamers.

But after 16 years of successful research, Anderson describes UW-Madison’s fusion research program as at a crossroads. He and his colleagues would like to build another stellarator—and in their view, bigger is most definitely better.

“We’ve shown with the HSX that for electrons, the confinement predictions are borne out,” Anderson says.

The HSX program is presently addressing other critical issues for fusion such as turbulence and plasma edge physics. “But for fusion you need hot ions, and that requires a physically larger machine, as nuclei are much more massive than electrons. We need a larger-scale experiment to address this.”

He says a larger experiment could draw the university’s diverse fusion programs—in the departments of physics, electrical and computer engineering, and engineering physics—into one large experiment with a much wider scope. A large steady-state stellarator has come online in Germany, and UW-Madison graduate students and scientists have already traveled there to collaborate in research. The German stellarator was designed based on physics known in the 1980’s; Wisconsin researchers want to take advantage of more recent breakthroughs in science and advanced manufacturing. They have been in conversation with the U.S. Department of Energy—and those talks have been positive so far in regard to the possibility of building a larger and more advanced version of HSX.

The machine Anderson envisions would have quite the price tag attached to it—$50 to $100 million—and would take six or seven years to build. However, Anderson notes that if the United States wants to remain on par with European and Asian countries in the development of fusion research, it essentially has no choice but to make that type of investment somewhere. And in Anderson’s mind, UW-Madison is the obvious place to make it.

“Since the 1960s, Wisconsin has been a key leader in fusion research and the premiere university plasma physics research locale in the U.S.,” Anderson says.

Investing in a larger stellarator would help cement the university’s legacy, he adds.