Nov 20, 2018

Ep 123: Dennis Whyte - Head of Nuclear Department, MIT

Head of Nuclear Department
Massachusetts Institute of Technology
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Show notes

1 -

Bret Kugelmass: Tell me about your backstory.

Dennis Whyte: Dennis Whyte grew up in a remote location in Saskatchewan, Canada. He loved math and science and always knew that he wanted to be a scientist involved in exploration. Whyte was interested in fusion early on, reading Popular Science papers and writing his physics term paper on the topic. He studied engineering physics at the University of Saskatchewan, which had a small plasma program, focusing on mostly atmospheric plasmas. During his last semester of his senior year, Whyte got a recommendation from a professor to do graduate work at a new fusion lab outside of Montreal. A tokamak is a donut-shaped chamber with magnets, which is one of the most popular devices used to study fusion and make fusion happen. This program was hosted at an industrial laboratory, Hydro-Québec’s research facility. The plasma physics discipline is most commonly associated with fusion. Plasma is a phase of matter. If gases are heated past 5,000-10,000 degrees, they become a plasma. The center of the Sun if 15 million degrees and is where fusion occurs. Fission is when a neutron splits apart an unstable atom, like uranium, and releases energy. Fusion happens when the lightest nuclei, hydrogen and its isotopes are forced to create helium by getting the nuclei close to each other. Both have positive charges, so they repel each other and must be accelerated and slammed into a target. The probability of fusion occuring is very small.

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Bret Kugelmass: If two particles are not hot enough or fast enough, do they just dissipate energy instead of fusing together?

Dennis Whyte: Yes, every particle has very high average kinetic energy. The center of a star is 15-20 million degrees, which is hot enough that the particles exchange kinetic energy. On Earth, a temperature of 100 million degrees is required to make fusion. A different fusion process is used than that of stars. Stars are extraordinarily good containers of energy and acts as an enormous gravitational container. When a fusion reaction occurs in the center of the Sun, huge amounts of energy are released, which eventually leaves as light. Stars don’t make a lot of power for how big they are, averating one watt for one cubic meter in the Sun. On Earth, the goal is many millions of watts per cubic meter. The power density is the most attractive part of fusion. The relative environmental footprint is reduced and in the end becomes a challenge of low power density sources, like renewables. Within a week of being in a research lab, Dennis Whyte knew it was what he was going to do for the rest of his life. Whyte received a national grant from the Canadian government as a post-doc which encouraged him to go outside Canada to gain experience. He went to San Diego where the General Atomics experiment D3D on a tokamak was ongoing. Canada then cancelled their fusion program, so Whyte stayed in the United States. He wanted to have the intellectual freedom that comes with being an academic, to pursue his own ideas in a way that wasn’t possible as a more structured research scientist. He wasn’t as motivated about the student at first, but discovered he loved teaching. Becoming a teacher made Whyte a better researcher. The exercise of explaining the fundamentals to students led to ideas and turned into big projects. Whyte spent four years at the University of Wisconsin, but he missed being in a bigger team and working on the applied part of research. Whyte moved to MIT because of its Plasma Science & Fusion Center, of which he is now the director. Whyte has been at MIT for 12 years.

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Bret Kugelmass: What did the plasma program look like when you first got to MIT versus what it looks like today?

Dennis Whyte: The specialty of MIT’s fusion program has always been built around magnet technology. Because of the expertise present, they had the ability to make magnetic fields that were much stronger than other laboratories were considering. By some basic arguments, they made the device smaller, which became Alcator. When Dennis Whyte first went to MIT, Alcator C-Mod was the third iteration of the fusion experiment. The focus of the program was education and training. It was solely funded through the Department of Energy and the program stopped a couple years ago. On the last day of its operation, it set a world record for fusion performance by surpassing 2 atmospheres of pressure in a plasma that was significantly hotter than the center of the sun. Doubling the pressure seen in other devices quadruples the energy density, making it more economical. Magnetic fields exert a magnetostatic pressure that is counteracting or containing the plasma. The material of challenge for the hot part of the fusion is that there can’t be any materials around. The plasma is tricked into thinking it’s not on Earth by creating a vacuum inside the donut and turning on the magnetic field. Nothing physically contacts the plasma, otherwise the plasma would become cold.

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