The Max Planck Institute of Plasma Physics is a German physics institute dedicated to the exploration of plasma physics for potential use in the creation of commercial fusion power reactors. It is an institute of the Max Planck Society and has two sites; one in Garching near Munich and one in Greifswald. It is host to several large experimental devices including the experimental tokamak ASDEX Upgrade, the experimental stellarator Wendelstein 7-AS, the experimental stellarator Wendelstein 7-X, and a tandem accelerator.
It is designed to advance stellarator technology and evaluate the major components of a possible future fusion power reactor. As of 2015, it was the biggest stellarator in the world. The researchers are hoping to be able to demonstrate thirty minutes of continuous operations, a crucial milestone on the way to commercial fusion power. Earlier tests of the Wendelstein 7-X resulted in world records for highest temperature, greatest plasma density, longest pulses and fusion products.
The term “fusion product” is the mathematical product of the temperature of a plasma, the density of the plasma and the energy confinement times. This product is a measure of how close a device is to achieving a nuclear fusion reaction.
A stellarator is a device that is designed to confine hot plasma with magnetic fields for the purpose of creating a controlled nuclear fusion reaction. In the toroidal fusion machines called tokamaks, instabilities develop in the donut shaped confinement chamber. The stellarator was designed to eliminate such instabilities by creating magnetic fields that force the particles traveling around the circular containment vessel to travel in twisted paths. The “magnetic cage” of the Wendelstein 7-X is created by a ring of fifty superconducting coils that are each about eleven and a half feet tall. Their exact shapes are the result of extensive optimization calculations.
Since the previous round of tests, the Wendelstein 7-X has had the walls of its containment vessel covered in graphite tiles. This will permit higher temperatures and longer plasma discharges. Plasmas of up to twenty-six seconds are now being produced. The plasma can be fed with a heating energy of seventy-five megajoules which is almost eighteen times the heating energy that was possible before the new graphite wall tiles were installed.
The latest fusion product for the Wendelstein 7-X stellarator encourages the researchers to believe that they are on the right track. Dr. Andreas Dinklage, the first author of the report on the new experiments said, "Thus, already during the first experimentation phase important aspects of the optimization could be verified. More exact and systematic evaluation will ensue in further experiments at much higher heating power and higher plasma pressure."
Since the end of 2017, the Wendelstein 7-X has received additional upgrades. New measuring equipment and heating systems have been added. Plasma experiments will begin again in July of this year. Major extensions are scheduled for the fall of 2018. The graphite wall tiles will be replaced by carbon-reinforced carbon components that are water-cooled.
The Wendelstein 7-X is not designed to actually produce more energy than it consumes. Part of the reason for the new experiments is to prove that the stellarator approach can yield fusion products equal to or better than the tokamak approach to controlled nuclear fusion.