Thomas Jarboe, a University of Washington (UW) professor of aeronautics and astronautics with Brian Nelson, research associate professor of electrical engineering; and research associate Brian Victor, research scientists David Ennis, Nathaniel Hicks, George Marklin and Roger Smith and graduate students Chris Hansen, Aaron Hossack, Cihan Ackay and Kyle Morgan, all in UW aeronautics and astronautics are using two handle-shaped coils to alternately generate currents on either side of the central core of a plasma chamber.
This idea competes with the tokamak, the donut idea that has the plasma swirling around inside. The ITER tokamak in France is a multibillion-dollar fusion reactor built to see whether a big enough reactor can generate fusion power by injecting high-frequency electromagnetic waves and high-speed hydrogen ions to contain and sustain the plasma by maintaining a hot 100-million-degree operating temperature while enclosing it with magnetic fields.
Plasma is difficult stuff. It’s so hot that the electrons have separated from the fuel’s atomic nuclei. The plasma cannot touch any chamber walls, so instead its contained by a magnetic bottle effect. Keeping the plasma hot enough and sustaining those magnetic fields requires a lot of energy.
The problem remains, crushing and smashing the atoms together takes a lot of energy, and scientists are still working on a way to do it so you get out more energy than you put in. The sun for example is a powerful fusion reactor but scientists haven’t recreated a full-scale sun here on Earth.
Professor Jarboe said, “That method works, but it’s extremely inefficient and expensive, to the point that it really is a major problem with magnetic confinement.”
The team’s research could help contain and stabilize the plasma using as little as 1% of the energy required by current methods. Jarboe presented the findings last week at the International Atomic Energy Association’s 24th annual Fusion Energy Conference in San Diego.
The new UW equipment looks like two handles from coffee mugs – except they are attached to a vessel containing a million-degree plasma that is literally too hot to handle. Essentially the magnets are simple horseshoe designs facing each other with a 90º offset.
The result is a stable equilibrium – if disturbed the fields will tend to come back toward the original state, like a ball resting at the bottom of a bowl that will settle back where it started.
Jarboe explains, “Here we imposed the asymmetric field, so the plasma doesn’t have to go unstable in order for us to drive the current. We’ve shown that we can sustain a stable equilibrium and we can control the plasma, which means the bottle will be able to hold more plasma.”
The UW apparatus’ two horseshoe-shaped coils alternately generate currents on either side of the central core, thus an imposed dynamo current drive. Results show the plasma is stable and the method is energy-efficient.
But the UW research reactor is too small to fully contain the plasma without some escaping as a gas. Next, the team hopes to attach the device to a larger reactor to see if it can maintain a sufficiently tight magnetic bottle.
Jarboe’s team has worked two decades on “helicity injection” where spirals in the plasma produce asymmetric currents that generate the right electric and magnetic fields to heat and confine the contents as a more efficient alternative. But the idea couldn’t be made stable. The results showed the UW strategy required less energy than other methods, but the system was unstable; meaning that if conditions changed it would wobble out of control. It’s like a stick balancing on one end, which is stable in one moment, but is likely to come crashing down with any nudge.
It seems Jarboe and his team has explored plasma handling pretty thoroughly. If “Big Fusion” such as the ITER program has any hope of ever getting to net power some incredibly innovative ideas are going to have to be integrated.
The Jarboe team may well be on to something worth an intense look. The tokamak has a complex confinement shape to try to control while the UW IDCD is a far simpler confinement shape.
Both IDCD and the tokamak rely on magnetic fields to crush the plasma into fusion – an idea that tries the common sense. But the IDCD looks like a much more manageable and probable way to get plasma atoms to join up and spill off energy.
An IDCD also looks like something a utility company could run.
Jarboe and company are off on a good research path. The science in magnets may be all that’s stands in the way of some success. It’s quite a relief to see something that might make big fusion possible instead of looking like history’s most stupendous boondoggle.