The hottest Spot

Bringing the Sun's fire to Earth - scientists at the IPP in Garching attempt no less. The research facility boasts temperatures of 100 million degrees Celsius. To prevent the interior of the facility from cooling down, it is maintained floating without contact by magnetic fields

The hottest spot in the Helmholtz universe is located in Garching outside Munich. The fusion facility of the Max Planck Institute for Plasma Physics (IPP) achieves temperatures of 100 million degrees Celsius – ten times more than inside the Sun. These extreme temperatures are necessary to induce nuclear fusion. A so-called plasma results: an ultra-thin gas that no longer consists of complete atoms, but within which nuclei and electrons whiz about separately. In this state, the nuclei have sufficient energy for fusion. The hot plasma cannot be contained in vessels made of any kind of material. Any contact with the outer shell would cool it down. This is why magnetic fields keep the plasma afloat.

Ultimately, nuclear fusion is the source of all forms of energy we use on Earth: in the Sun, hydrogen nuclei (protons) fuse, creating helium nuclei. In sum, the end products are slightly lighter than the starting products. The "lost" mass has been transformed into energy, following Einstein's formula E = mc². The scientists in Garching attempt to simulate the Sun's fire on Earth and to harness this energy.

This creates enormous challenges. A particular difficulty is the construction of the "magnetic cage" containing the plasma and thermally isolating it from the environment; the large coils must be correctly arranged and configured. Resulting from the researchers' calculations and refinements are the sometimes bizarre shapes of plasma vessels (Image: Wendelstein). To bring the gas in vacuum to such high temperatures, hydrogen atoms are shot into the reactor vessel with high energy, where by collision they release their energy to the particles within the plasma. In addition, microwaves heat up the plasma, much like a pizza in the microwave oven.

The aim of this research is to create a fusion power plant. The advantages of this technology are evident: no emissions harming the climate, unlimited fuel resources and no danger of uncontrollable chain reactions as is the case with nuclear fission. In summer next year, construction of a new research facility, Wendelstein 7-X, will be completed at the IPP's branch institute in Greifswald. In the south of France, the hitherto largest fusion research facility is being built in international co-operation. This test reactor, called "ITER", is to demonstrate for the first time that fusion can generate energy. 

However, the question of what is normal and what is an extreme remains relative. Under conditions on Earth, matter exists almost exclusively in solid, liquid or gaseous state – depending on temperature. When looking up to the night sky, we see stars, that is, matter in form of fusion plasma. This comprises the greater part of visible matter in the cosmos. Given this view, the conditions in the Garching fusion facility are the norm and the conditions elsewhere on Earth are "extreme".

29.10.2013 , Martin Trinkaus

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