Test of the EURATOM LCT coil (NbTi conductor) with forced flow He II cooling

The EURATOM LCT coil, a D shaped NbTi coil, was tested in the TOSKA facility at Forschungszentrum Karlsruhe with pressurized forced flow He II cooling. A suitable cryogenic system based on an existing 1.8 K He II 300 W liquifier was designed for cooling the coil by pressurized forced flow He II circulated by pumps across heat exchangers immersed in a He II bath. Three types of pumps (piston, centrifugal, thermomechanical) were used. The cryogenic system worked well under usual operation and fault conditions. No significant differences were found between He I and He II forced flow cooling. The D-shaped coil was reinforced by stainless steel belts keeping the D shape in single coil operation mode. No backlash was found between the coil and its reinforcement structure in agreement with predictions of the finite element analysis. The coil achieved ∝11 T as predicted from single strand measurements and previous tests in the frame of the large coil programme. The results are an encouraging step in using this technology in large superconducting magnet systems for magnetic confinement in fusion research. (orig.)