Now successfully completed is the first of several cooperation projects that are to involve Poland’s fusion research programme in Wendelstein 7-X, the device now being built at Max Planck Institute for Plasma Physics (IPP) in Greifswald. Since 2006, technicians and engineers from the Polish Academy of Sciences in Cracow – specializing in superconductivity technology – have put in thousands of work hours to assemble Wendelstein 7-X. Along with other projects, Poland is thereby contributing a total of 6.5 million euros to the fusion device. In reciprocation, Polish scientists have been made partners in the Wendelstein 7-X research programme.
Difficult connection: specialists from Cracow doing the tricky manual installation of the complex superconducting coils of Wendelstein 7-X (photo: IPP, Anja Richter-Ullmann)
The aim of fusion research is to develop a power plant that, like the sun, derives energy from fusion of atomic nuclei. To do this, the fuel – an ionized low-density gas, a plasma – has to be confined with almost no contact in a magnetic field cage and then heated to ignition temperatures exceeding 100 million degrees. Once completed, the Wendelstein 7 X fusion device, now being built at Max Planck Institute for Plasma Physics in Greifswald, will be the world’s largest and most modern device of the stellarator type. Its magnetic field makes continuous operation possible in a simple way.
The magnetic cage is generated by a wreath of 50 bizarrely-shaped magnet coils, these being the technical core of the device. When these are cooled to the superconducting temperature, close to absolute zero, the current later flowing through them will suffer almost no loss. They are wound from a finger-thick cable whose aluminium sheath encloses a flex of thin copper wires in which the superconducting niobium titanium strands – the actual conductors – are embedded. Supercold liquid helium as coolant will later flow in the space between the individual wires and the sheath.
Superconductivity specialists at the Institute of Nuclear Physics of the Polish Academy of Sciences at Cracow took on the tricky job of interconnecting the coils. Jülich Research Centre provided the necessary connecting pieces – rigid, up to 14 metres long superconductors, delivered already in their final form. Once unpacked, the unwieldy conductors presented some challenge in getting them transported into the assembly hall. Finally, helium-filled balloons were enlisted to levitate the sensitive components carefully into the hall. Up to 45 technicians and engineers from Cracow were occupied at Greifswald for six years in interconnecting the coils with a total of 121 conductors by means of 240 joints and 400 support elements, likewise produced at Jülich.
Helium-filled balloons were enlisted to levitate the sensitive superconductors carefully into the hall. (photo: IPP, Antje Lorenz)
After more than 160 man-years of work the last coil connection is linked, insulated against high voltage and checked for helium tightness. “We are most grateful for this excellent achievement and look forward to further cooperation”, stated Project Head Prof. Dr. Thomas Klinger on completion of this complicated mounting procedure. Now that the Cracow specialists have departed from Greifswald, cooperation is being continued with the National Centre for Nuclear Research at Swierk in Poland: The accelerator specialists are occupied with production of components for the neutral-particle heating in Wendelstein 7-X. This will heat the plasma by injecting fast particles into it. The production orders have already been placed with Polish and other European industrial concerns.
Two-thirds of the cost of the two projects is being met by the Polish Ministry of Science, who want to develop their fusion research programme around Wendelstein 7-X. In addition, IPP-financed cooperation projects for plasma diagnostics with the Universities of Warsaw and Opole are planned. “With their contributions of personnel from Cracow and Swierk the Polish Science Ministry are providing a total of 6.5 million euros for Wendelstein 7-X”, states Prof. Klinger. “This makes Poland, after the USA*, the second largest contributor to Wendelstein 7-X.”
* see IPP Press Release 8/2011