Posted on: 26th March 2014

IPP scientist Gregor Birkenmeier built this device for his PhD Thesis at the plasma physics department at Stuttgart University. It measures plasma turbulence inside the small stellarator TJ-K, which the institute operates. “The good thing about a small experiment is that scientists and students can lay their hands on it to test new diagnostic devices, for instance”, says Birkenmeier. The ring measures 35 centimetres in diameter and is fixed to the stellarator wall in a way that the 64 tungsten rods –Langmuir probes – poke from all sides into the edge plasma. They measure density and potential fluctuations in the plasma, parameters from which plasma turbulence can be deducted. The attached cables transmit the signals. The measurements yielded valuable results for the advanced stellarator Wendelstein 7-X, which is under construction in Greifswald, Germany. They experimentally confirm, for instance, that plasma turbulence does depend on the geometry of the plasma cross section, which strongly varies in Wendelstein 7-X. In June 2013, Max Planck Society honoured Gregor Birkenmeier for his work with the Otto Hahn Medal for outstanding scientific achievements.

The Max-Planck-Institute for Plasma Physics is one of three German Research Units in the European Fusion Programme.