Tokamaks, spheromaks and stellarators- oh my!
Yesterday evening, Al Bloom welcomed scientists from the US and Japan to a symposium on fusion energy research. After a brief introduction to atomic physics by Swarthmore Professor Michael Brown, presentations were given by Professor Yasushi Ono from the University of Tokyo and Professor Loren Steinhauer of the University of Washington.
The talks focused on the history of fusion research, the current state of technology and what needs to be accomplished before fusion energy can become a viable power supply. Additional (more technical) events for this weekend can be found on Professor Brown's website.
"The current age of oil use is special, as the world will soon no longer have oil to use," said Brown in his introduction. Because fusion uses deuterium (naturally occurring hydrogen with an extra neutron) as fuel, an electric grid based on fusion would have a minimal effect on the environment. Deuterium is heated until its break free of their nuclei (forming plasma), which then fuse together to form helium, thus emitting additional energy.
In answer to a later question, Brown stated the ratio of energy required to create and contain the plasma where nuclear fusion takes place to the energy produced is currently about 1:1. Additionally, the cost of creating fusion is still higher than the value of the electricity produced. In other words, the realization of a clean renewable resource is still a ways off. It was towards that goal that Swarthmore hosted this symposium.
The area of nuclear fusion deemed most promising (by politicians holding federal purse-strings) includes fusion that takes place in toroidal, or donut-shaped, clouds of plasma. The focus of Professor Ono's and Professor Steinhauer's research is several types of fusion that take place in non-toroidal shapes. The history of this part of the field, "is like Jurassic Park," began Ono. In the 80s there existed many non-toroidal fusion reactor ìdinosaurs,î each species pursuing the goal of renewable energy. Then the meteor struck when the US government concentrated research funding elsewhere. "Now we're back! This time as a full-grown Tyrannosaurus Rex."
As the Cretaceous period ended in the US and the fall of the Soviet Union put Russia economically out of the game, Japan became a hub of research into alternative concepts for nuclear fusion. Professor Ono continued by comparing the efficiency and cost of different forms of fusion Japan has experimented with. In particular, a reactor has been built that creates plasma and blows it into a chamber so as to create a torus, just as a smoke-ring is created. Two of these smoke-rings are smashed together, forming a spherical cloud of plasma capable of sustaining fusion for greater periods of time. Research like Professor Ono's is now regerminating interest in the United States.
Professor Steinhauer began with an explanation that, as a theorist, he wouldn't have any interesting pictures. Instead he had prepared highly amusing cartoons to illustrate the abstract concepts of nuclear fusion. "You have to think outside of the torus," said Steinhauer before presenting the alternatives: pumpkins and zucchinis. The audience laughed throughout the speech as smashing pumpkins gave rise to non-tilting zucchinis, all clearly drawn in Microsoft Paint.
With the use of these squash analogies, detailed how the work of experimentalists and theorist are working together to understand what occurs inside such things and Spheromaks (pumpkins) and Field-Reversed Configurations (zucchinis). These formations of plasma would lose energy and fall apart if scientists poked them with instruments. Therefore, understanding them theoretically has faced some surprises. The opening event of Swarthmore's US/Japan Symposium on Fusion Research was interesting, humorous, and informative to all who attended.
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