What other process involves nuclear fusion

Nuclear fusion: how is Iter doing - and are the Chinese overtaking us?

Those responsible would like to decide by 2020 whether they will actually build the CFETR and would then be ready to put it into operation by 2030.

And what is the difference between the CFETR and the ITER?

ITER is an experiment with which those involved want to show that the fusion process can be kept alive by the self-generated energy. As a result, the plasma heating can be shut down again after the initial ignition. In contrast to this, the CFETR experiment is designed in such a way that more powerful additional heating is required - the physics, i.e. the self-preservation of the fusion reactions, is not in the foreground. To do this, the Chinese are trying to use the CFETR to take technological steps that ITER is not aiming for. For example, ITER will buy the tritium needed for the fusion reaction and not produce it itself. CFETR, on the other hand, is supposed to close the cycle and generate tritium from lithium, so that the process is complete in itself.

Does that mean ITER would also benefit from the findings made at CFETR?

Yes, sure. There is collaboration and everyone involved benefits from one another. In a way, the CFETR is already the step we want to take with DEMO. CFETR contains the functions of DEMO, so that with the knowledge of ITER and CFETR one would no longer need a DEMO, but could build a functioning fusion power plant straight away.

So - if nuclear fusion can really be tamed on Earth and everything works out - one could perhaps count on functioning fusion power plants earlier?

At least it could be that the construction of a fusion power plant - maybe several - will start in China around the year 2040. It may take until 2050 for these to actually deliver electricity.

Together with a private company, MIT wants to build a functioning, very compact reactor, the so-called SPARC, in around 15 years. Then the Americans are more likely to win the race?

It's a great project. But that they will go online in 15 years - as already stated in press releases - is, in my opinion, unrealistic. And if the principle actually works, that does not mean that ITER can pack in, but - and this is what the parties say themselves - that the project should be understood as synergistic with ITER. We are cooperating with this project, and personally I actually find it very exciting.

What exactly are the Americans doing?

They are trying to produce coils using new types of high-temperature superconductors, with which a significantly higher magnetic field can be generated than we can with our experiments. If that actually works, the systems can be made much more compact, which probably also makes them cheaper.

"In my opinion, the American colleagues are exaggerating a little"

Compared to the technology that is being tested at ITER: How much smaller could such a reactor be?

In my opinion, the American colleagues are exaggerating a little. They claim that the reactor would then only have a radius of three meters, ITER has six. And the DEMO fusion power plant would have a total radius of eight and a half meters. If I assume that I can reach the high magnetic fields, I get to around five meters - I think three is unrealistic.

And what is different about the superconductors at MIT from yours at ITER?

With superconductors there is a critical magnetic field and current strength above which the conductivity returns to the normally conductive state. With the new superconductors, this value is relatively large, so that you can work with stronger magnetic fields. It has already been shown on a small scale that these superconductors can be manufactured. Now comes the more exciting part: enormous forces act on the magnetic coils. The current coil designs can just about compensate for this. However, if you make the field stronger now, the forces acting will also increase. The question is: How do you make a structure around the outside with affordable material that can handle the higher forces and that ensures that the coil does not dissolve? This is what our American colleagues are researching.

In America there is another well-known player in the field of fusion energy with the company Lockheed Martin. It also plans to build a compact fusion reactor, the Compact Fusion Reactor (CFR). What do you make of it?

We'll look at that, of course. They made a big stir in 2015. If you read the press release carefully, it just said that they were looking for someone to pay for the merger project. According to the patent and the little that can be found on the Internet, they want to combine two concepts. We both know that they don't work really well. How they want to solve the known problems of poor thermal insulation and the high local stress on wall components is not discussed at any point. Overall, I don't think the whole thing is particularly serious. There are better projects with really good scientists. But then they also admit that they run a very high risk that it might not work - but you still want to try it.

"I won't see anyone on the network before 2050, and then only the Chinese"

So "high-risk-high-gain" projects?

Exactly. And of course we discuss with those involved as long as they put the facts on the table. However, this is not the case with Lockheed Martin. That is why I cannot allow myself a final judgment about your project.

Do you think that at some point we will have Fusion Stream in Germany, and if so, how much longer do you think it will be?

Well, I think it's pretty realistic that we can achieve a positive energy balance with ITER. That's also the part that we kind of promised - to show that nuclear fusion can basically be an energy source. It is very difficult to estimate whether the entire technology that goes with it will have been developed in 30 or 40 years in such a way that a functioning system can be produced for a moderate price. At the moment you don't see any fundamental obstacle; however, there is still a long way to go. In any case, I won't see anyone on the network before 2050, and then only the Chinese for the time being. This is simply because the suffering in Europe is currently not so great that a fusion power plant urgently needs to be developed.

In view of the numerous renewable energy sources: do we even need fusion reactors?

We are already in the process of converting the energy system and have a number of ideas on how this could work. However, I am of the opinion that we do not yet have a silver bullet for the energy problem of the future. What bothers me is that some claim they have the answer and therefore argue that fusion research or other technologies don't need funding. We need different concepts, and at some point it will be a social process which technologies one ultimately opts for. To say today that we have already dealt with the subject is negligent. If we in Germany manage to convert the energy system to renewable sources by 2030, that would of course be nice. But the music doesn't just play with us. We cannot just look at Germany or Europe, we have to keep an eye on all world events.