High temperature superconducting levitation coil for the Levitated Dipole Experiment (LDX)

The Levitated Dipole Experiment (LDX) is an innovative approach to explore the magnetic confinement of fusion plasmas. A superconducting solenoid (floating coil) is magnetically levitated for up to 8 hours in the center of a 5-meter diameter vacuum vessel. This coil is supported by a levitating coil (L-Coil) on top of the vacuum vessel. In the initial machine design, this levitating coil was a water-cooled copper solenoid, and was the experiment's single largest load on the available water system. The main benefit of using a high temperature superconducting coil is the ability to apply more auxiliary heating power to the plasma. However, this coil will also be the first high temperature superconducting coil to be used in a US fusion program experiment. The high temperature superconducting L-Coil is a solenoid, using a two-in-hand winding of a commercially available 0.17 mm/spl times/3.1 mm tape by American Superconductor Corporation with a critical current of 62 A at 77 K and self-field. The L-Coil will be operated at 0.9 T and 20 K. The L-Coil has a protection circuit that not only protects it against overheating in the event of quench, but also against F-Coil collision in the event of a control failure.