A Q&A With the Director of the Princeton Plasma Physics Laboratory, Dr. Stewart Prager

PPPL February 2, 2016

stewart prager

(Photo by Elle Starkman/ PPPL Office of Communications) Stewart Prager

Q: What is fusion and how can it produce energy?

A: Fusion is the energy source of our sun and the stars. In a fusion reaction, two atomic nuclei fuse and produce very fast-moving particles. Billions of such reactions occurring in a hot gas of electrically-charged particles, a plasma, produce substantial heat. So a reactor produces heat from fusion using hot plasma. The heat then can be converted to electricity. Essentially, we would be producing a “star on earth,” taking its energy, converting it to steam and generating electricity.

Q: Why is it so hard to create fusion energy on earth?

A: It’s difficult because it requires making a hot gas – plasma – that is 10 times hotter than the core of the sun – 100 million degrees – and confining it for long periods. And you have an enormous engineering challenge to surround this plasma by a material structure. Fusion is one of the most difficult science and engineering challenges ever undertaken.

We’ve had to create an entirely new field of science – plasma physics – in order to make progress on this opportunity. And here at Princeton, we are expert in plasma physics, as well as fusion engineering.

Q: What are other benefits of fusion energy research?

A: The plasma science we’ve learned has enormous applications. Plasma TVs, computer chips, efficient lighting, a way to burn waste, to treat wounds, and to power rockets are some of the practical applications this research has spawned. Of course, most of the visible universe is made of plasma, so this research advances tremendously our understanding of the cosmos.

Q: Is commercially viable fusion energy achievable?

A: Yes. We can routinely produce plasmas as hot as hundreds of millions of degrees and control them with finesse. We’re building an international experimental reactor in France to demonstrate much of the scientific and technological feasibility of a large fusion reactor, by producing 500 million watts of fusion power — 10 times more energy than it will take to create the power. PPPL is a U.S. contributor to this enormous international project. Commercial fusion energy is certainly achievable.

Q: So commercial fusion reactors will exist?

A: If we as a nation continue to have a commitment to fusion energy, yes, commercial fusion reactors will exist. But we must commit to the experimental steps that will take us to commercial reactors. Many institutions in the United States have made seminal contributions to fusion, and the Princeton Plasma Physics Laboratory is a leader in the frontier research that is critical to the understanding and future of fusion.