A new feedback system will help scientists better control the plasma in fusion devices.
Nuclear fusion is a promising technology which if perfected, could provide Earth with an unlimited amount of free and clean energy. One of the problems with building a fusion device however, is that it requires an immense amount of energy to heat a gas to a super-hot plasma state, and then very precise tools to help control that plasma. Powerful magnetic fields and particle beams are used to control and shape the plasma, and now, researchers have developed a system to provide real-time feedback and control of these tools, in a doughnut shaped reactor known as a tokamak.
“When designing fusion machines, it’s becoming more and more important to use control systems and modeling techniques taken from the world of aeronautics engineering,” said Imène Goumiri, the scientist who led the work. “What’s new is that these tools have now been applied to plasma physics problems; that’s what makes this research unique.”
The new feedback controller gathers information from a range of sensors inside the tokamak. This data is then interpreted through a series of computer algorithms. The algorithms use the current and past information of what has happened with the plasma to predict what’s going to happen with it in the future. It then actuates six neutral particle emitters inside the reactor, as well as six magnetic coils on the outside, to manipulate the plasma. “This is the first time these two actuators have been used together to control the plasma rotation profile,” said Steven Sabbagh, a senior research scientist and adjunct professor of applied physics at Columbia University.
Controlling the rotation profile prevents the magnetic field inside the tokamak from degrading, and thus prevents the plasma from dissipating. The algorithm also balances the effect of the magnets and neutral beams to ensure that the plasma doesn’t suddenly shift from one speed to another, but maintains smooth transitions . The ultimate aim is to achieve a particular plasma energy and rotation.
The research team hopes that once implemented, the new algorithms can provide information for scientists like Goumiri that will allow for improvements in future designs. Goumiri believes future plasma reactors will incorporate more and more algorithms and controllers.