Speaker
Chandra Prakash Dhard
(Max-Planck-Institut fuer Plasmaphysik)
Description
On 13thth February 2015 began the cool-down of about 450 tons cold mass of Wendelstein 7-X i.e. 70 superconducting magnets, 14 currents leads, massive support structure and the thermal shield, enclosed within a vacuum vessel of about 15.4 m outer diameter. After a smooth cool-down, the temperatures around 5 K, within the so called Short Standby Mode with the thermal shield return temperature < 70 K, were achieved on 9thth March 2015. Since then, for about 1 year, these components are kept cold at different temperatures within various operating modes of helium refrigerator. The refrigerator is sized to provide an equivalent cooling power of 7 kW at 4.5 K with the help of 2 screw compressors consuming 1.6 MW electrical power, 7 turbines, 2 cold compressor and 4 cold circulators. In the Standard Mode (SM), the supply temperatures were reduced to 3.9 K using the cold compressor and the mass flows were increased to 200 g/s through the magnets and 300 g/s via the magnet casings and structure with the help of cold circulators. The commissioning of magnets with currents up to 13.4 kA and the plasma operations with about 2.5 T magnetic field (with different currents in non planar and planar magnets) were carried out in the SM. Over the Christmas vacations, the temperatures were raised to 100 K within so called Long Standby Mode. The refrigerator operation was optimized for each of these modes by achieving the guarantee values of mass flow, pressures and temperatures. The details of the refrigerator operation at different modes, operation conditions of main equipments, failures, repairs etc. shall be presented in the paper.
Co-authors
Chandra Prakash Dhard
(Max-Planck-Institut fuer Plasmaphysik, Greifswald, Germany)
Holger Bau
(Max-Planck-Institut fuer Plasmaphysik, Greifswald, Germany)
Michael Nagel
(Max-Planck-Institut fuer Plasmaphysik, Greifswald, Germany)
Sylvio Raatz
(Max-Planck-Institut fuer Plasmaphysik, Greifswald, Germany)
Thomas Rummel
(Max-Planck-Institut fuer Plasmaphysik, Greifswald, Germany)
Uwe Meyer
(Max-Planck-Institut fuer Plasmaphysik, Greifswald, Germany)
