"Fusion, in a way, is astrophysics in a box"

Less than half a year in his new position, he already explains the H-mode as if he never talked about anything else. On 1 November 2008 Günther Hasinger took up his appointment as Scientific Director of the Max Planck Institute of Plasma Physics (IPP) with its two institutes located in Garching and in Greifswald, Germany. The IPP hosts the tokamak ASDEX Upgrade and the Stellerator Wendelstein (W-7X). Günther Hasinger ranks amongst the world's leading capacities in the fields of cosmology and X-ray astronomy—the investigation of outer space in X-ray light. So far, exploring the universe was his passion, documented in his many scientific contributions and awards and finally in his book "Schicksal des Universums" (Fate of the Universe). Fusion has become his newest flame.

Newsline: From the stars to the energy of the stars—have you already settled into your new position?

Hasinger: Yes and no. I feel very happy and honoured to join the scientific community in its quest to develop a new source of energy, although I am still on a steep learning curve as in regards to the fusion vocabulary. And I have to admit that I was a bit nervous when I took over this position here in Garching. As former Director of the Astrophysical Institute in Potsdam near Berlin and until recently of the Max Planck Institute for extraterrestrial Physics in Garching I do have experience in leading big science labs, but the enterprise here is significantly larger.

What convinced you to swap from investigating black holes to studying plasma physics?

Being Director of the IPP, the biggest institute of the German Max Planck Society and also associated to the Helmholtz Association of large German research centres, represents a big challenge for any researcher. I also felt the responsibility to join in to help solving the global energy problem. Finally, astrophysics and fusion are not that far apart as you may think.

What would you say are the biggest challenges the fusion community in general and the IPP are currently facing?

Well, it has been proven that fusion works and that we can produce energy with it. The challenge now is to develop a working reactor concept. ASDEX Upgrade, JET and ITER together take a sort of "step-ladder-approach" to this. ITER, being an experimental reactor, will test different approaches and different operation scenarios. We are preparing these tests on a smaller scale. The ultimate goal is to prepare the ground for a demonstration power plant, DEMO.

Just to mention one of the many ITER-relevant experimental research issues we are dealing with here in Garching are the ELM control studies for ITER. These edge instabilities in the plasma represent a delicate balance between good and bad: they can clean the plasma, but also carry away the energy and thus pose a danger to the wall, in particular for ITER and DEMO. How to best control ELMs is one part of the research done here on ASDEX Upgrade.

Also, predictions of tokamak operation scenarios rely very much on a detailed comparison between experiments and theory and thus also on computational capacity. In this regards we have very good news: We have just launched a high-level scientific support group for the new High Performance Computer for Fusion (HPC-FF) that is going to be installed in Jülich. HPC will deliver computing power of about 100 teraflop/s and will certainly propel the simulation of fusion processes.

What about the stellerator, how is Wendelstein 7-X progressing?

I am glad to say that with Wendelstein 7-X we are on a stable track now. Over the past decade this experiment has faced many difficulties—technological but also in schedule and budget. Thanks to the tremendous efforts of the team under my predecessor, Alex Bradshaw, both schedule and cost have been stabilized since two years. We are optimistic that we will turn on the machine in 2014. Wendelstein 7-X will then be the most powerful stellarator, testing the optimized steady-state magnetic confinement scheme alternative to tokamaks like ITER.

Where does the stellerator stand compared to the tokamak?

The stellerator is one generation behind the tokamak. The difference between both technologies is the fact that a tokamak can, in principle, be designed on a drawing board. In order to design a stellerator, vast computational capacity is needed. That is why Wendelstein 7-X is often referred to as being a child of the Cray computer. Whereas ITER is crucial for proving that a fusion machine can produce more energy than it consumes, Wendelstein 7-X is to prove the reactor potential of the stellerator concept.

You mentioned earlier on that astrophysics and fusion are not that far apart. Could you please explain a little more?

I have spent part of my career helping to develop X-ray optics and X-ray detectors looking at the sky. To me, there are similarities between astrophysics and fusion plasmas: let's say, fusion is like the universe in a box. Inside that box it is extremely hot, around the wall moderately warm and on the outside, around the superconducting coils it is very close to absolute zero. The same holds for hot astrophysical plasmas, like supernova remnants or the gas in clusters of galaxies. For both you need a whole suite of multi-wavelength diagnostics, and thus there are synergies I would like to explore.

Very soon, in May, we will install a new working group here at the Technical University Munich and IPP called "Astrophysics and Plasma Diagnostics." This new group is intended to strengthen the ties between the IPP's core research on nuclear fusion and astrophysics. One goal of this new group will be the application of new detectors developed for X-ray astronomy to fusion devices, both to improve the readout speed for spectrometers and for hard X-ray imaging. My dream is to obtain a hard X-ray image of the plasma in ASDEX Upgrade. Besides, I guess I cannot completely give up looking for black holes.