The road to nowhere

An experts panel of 21 top scientists in the field of fusion research has recently met to assign new objectives to ITER and define a new roadmap: please have a look at the article on Nature here.

They are top-level researchers, engineers, directors of labs with a load of experience which completely crushes my modest know-how. And yet, I don’t understand what they try to do. Or I understand too much: they try to do politics.

To quickly summarize the new roadmap, they want to focus everything on achieving break-even with a gain factor of 10, i.e., you produce ten times more power than you feed in your tokamak. And to do that, they skip every physics experiments which were supposed to pave the way to this goal (well, they postpone these experiments until 2030). The idea is simple: we know how a tokamak work, we have an interpolation figure for the confinement time in function of the machine’s parameters; we just have to build it: this is an engineering problem. The physics will help in tuning the system.

This is a very risky bet. We are far from understanding all aspects of a fusion plasma, even on present machines. A simple example: the H-mode, which is an improved mode of confinement of the plasma. There is no accepted theory of it. The associated instabilities, the ELMs (Edge Localized Modes), are not completely understood. We throw all this problems in the freezer and say: no worry, we will take huge margins and we will manage to reach Q=10.

torus_transformer

This is a short-sighted approach, driven by the problems of funding: ITER managers need a quick visible result; something that will create the buzz, that will compete with the announcements of the NIF that they have already reached break-even. When I say quickly, the next opportunity is in 2027: this machine requires time to be built. But with this goal, you lose the big picture: ITER is supposed to provide the experimental foundations for a future power plant. And you get them by doing basic physics experiments. Even if they manage to achieve this primary goal, what will they do next? The physicists who were supposed to work as soon as 2020 will have to wait one more decade: they will not wait, they will go to other fields. In the end, you will have a machine for engineers with great chances that they do not understand, without the help of physicists, why it does not work.

I love plasma physics and fusion research: this is a beautiful area of physics; perhaps not so elegant as fundamental physics, but not so muddy as fluid mechanics: the plasma has a coherence that classical fluids do not have: you can elaborate nice theories of turbulence, gyrokinetics, hamiltonian and even better, you can see them in action in the tokamak. Huge progresses have been made since the concepts was proposed in the 50s. There still are some major hurdles and ITER, even if it was not the best choice, would have been a great tool to improve our knowledge. I fear that we are about to miss the moon.

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