Nuclear fusion – the process of recreating the reaction that powers the sun for unlimited energy – has been making large gains in the past few months. Most recently, the Max Planck Institute for Plasma Physics in Greifswald, Germany, has switched on their latest experimental reactor, Wendelstein 7-X. Daniel Andruczyk, a research professor of nuclear, plasma and radiological engineering at Illinois, worked on the predecessor to W7-X, WEGA, helping to develop some of the diagnostic, heating and control systems for the newer machine. He talked about the current state of fusion energy research with News Bureau physical sciences intern Austin Keating.
Could you explain what fusion is, and how the W7-X power-up this month is a step toward fusion energy?
The eventual goal in fusion is to have self-heating plasma, where it is hot enough from the reactions happening that we can switch off the external heating systems. We’re getting closer to this with machines such as W7-X coming online now and in the next decade.
When W7-X was activated recently, they were aiming for “first plasma.” It's just to say, “Are things working?” Nothing fancy, just running it for a second to make sure it works.
What’s the end goal for W7-X? Could it be the first sustained fusion reactor?
With W7-X, they’re aiming to achieve true steady state. They want to be able to operate the plasma at fusion-relevant parameters for 30 minutes or more. That’s what they’re going to be working on the next 10 to 15 years.
W7-X is obviously still an experimental machine. It's not a reactor in the true sense that you're going to get energy out of it. It's a proof of concept. If this works, then you have the next step where you build a prototype of a future power station. It's designed to put out more energy than what's put in – and fusion has so far not been able to do something like that.
What are some of the challenges that have made achieving fusion energy so elusive, and are we any closer to overcoming them?
One of the hurdles in fusion right now is the materials. The plasmas are heated up to over 100 million degrees, so you have this hot soup of plasma. The ions and electrons have a lot of energy from being that hot, so if they hit a surface within the machine, they're going to do a lot of damage to that surface. This throws up impurities into the plasma that affect the plasma’s performance, and results in damage where we have to shut a machine down to repair it.
One way to try to mitigate this is to build the machine big enough that the power loads on the walls are low enough for this not to be a problem. That’s why the International Thermonuclear Experimental Reactor is so big and expensive – $20 billion. They need to give the suspended plasma room to keep down the power loads on the surfaces.
Here at the Center for Plasma-Material Interaction at Illinois, we are researching ways to make the inner wall materials able to withstand the large power loads. One way is to make them from liquid metal, namely lithium. If we can achieve this, then the vacuum chamber can be smaller and the costs can start to be reduced.
The Max Planck Institute donated the W7-X predecessor that I worked on, WEGA, to the University of Illinois. We renamed it HIDRA. Once we get the main power systems operational on HIDRA in the next two or three months, we'll be able to start testing some of our ideas.
There's a running joke with fusion energy that it's always “30 years away.” What gives you hope?
Technology was never advanced enough for fusion until now. Today’s technology makes fusion really possible.
The first ideas and concepts of fusion actually came out in the 1930s. That was the first time scientists thought of using the fusion reactions, which power stars, for energy. In the '50s, everyone started to build these machines to try to do fusion. People came up with theories and started testing them. They'd heat up gas to get plasma, and then they’d get instabilities, and then they'd figure out how to stabilize it from there. New, unforeseen instabilities would always crop-up.
With ITER, we don’t quite know what it’s going to throw at us. For all we know, there could be a whole new physics regime behind getting plasma to the point that it’s so hot that it can heat itself. But all the evidence so far shows it will work – and that’s exciting because if fusion works, it will revolutionize mankind.
