Cambridge (MA) – MIT researchers have solved a major problem in the area of fusion power research – how to safely, accurately and in a controlled way, contain and stabilize the hot plasma core of a fusion reaction without losing heat or creating turbulence. While still “decades away,” according to researchers, from generating more power than it consumes, this latest research takes us over one huge hurdle and paves the way for France’s upcoming 10x larger fusion reactor, ITER.
Alcator C-Mod reactor
In operation since 1993, MIT’s Alcator C-Mod reactor has the highest magnetic field and plasma pressure of any fusion reactor in the world. It’s also the largest reactor operated by any university. It’s part of the Alcator Project in MIT’s Plasma Science and Fusion Center (PSFC). This latest research builds on the team’s multi-year effort in an attempt to find a reliable method of guiding, directing and containing the hot plasma core using radio waves.
By directing the newly discovered array of radio wave emissions at the extremely hot donut-shaped plasma core, which is millions of degrees Fahrenheit, MIT has now been able to encase it and make it stable. In fact, the data in their reactor indicates there’s enough stability to support France’s upcoming International Thermonuclear Experimental Reactor (ITER), which will be 10x larger than MIT’s. It is currently being built in France and will be operational before the year 2020.
Plasma in motion
Over the past few decades, several experiments around the world have been carried out in an attempt to find ways of moving plasma around inside the core vessel. They’ve looked for ways to do this in a way which do not lose heat and prevents turbulence, as turbulence reduces reactor efficiency.
The techniques employed prior to this latest discovery have long been known to be insufficient to power future reactor cores like the one being built in France.
The new findings are also quite surprising to many theoretical physicists. According to a lead physicist on the project, Yijun Lin, “Some of these results are surprising to theorists.” Co-lead on the project, John Rice, said, “…there is no satisfying theoretical foundation for why it works as it does. But the experimental results so far show that the method works, which could be crucial to the success of ITER and future power-generating fusion reactors. Lack of a controllable mechanism for propelling the plasma around the reactor is potentially a showstopper.”
One interesting aspect is the potential danger should plasma escape the field. Were its high energy electrons able to touch the steel walls of the inner chamber, for example, they would melt through it like butter. While this poses no risk to the operators as there is more than sufficient shielding, it does damage hardware.
To keep this from happening, researchers discovered that quenching the space around the core with argon or neon gas causes the plasma to convert its high heat directly into light. When this happens, for about one thousandth of a second, it becomes the brightest source of light on the planet – equivalent to roughly 1/1000th the total output energy of the entire United States in a single light source. This one-billion-watt light-bulb is contained within the core, however, and is not visible outside.
The reactor being built in France, which has a 10x larger core, will emit 1000x more light than MIT’s reactor. This will make its millisecond light emission equivalent to the total energy output of the entire United States, roughly one trillion watts.
Read more on MIT’s press release.