Design and First Tests of a 800 kJ HTS SMES

The SMES is an interesting way for a large power pulsed source. High critical temperature superconductors have brought the possibility to operate at higher temperatures when compared to conventional NbTi SMES. This makes cryogenics easier, enhances the coil stability and improves the power. In a context of a DGA (Delegation Generale pour l'Armement) project, we have fully designed and partly constructed a 800 kJ SMES. The coil is wound with Nexans Bi-2212 PIT conductor made of 3 or 4 PIT tapes soldered in parallel depending on the magnetic flux density. At some locations the conductor is reinforced by a stainless steel tape. The conductor is isolated with Kapton. The coil consists in 26 superposed simple pancakes wound and glued on cut and epoxy coated copper plates. The rated current is 315 A for an energy of 814 kJ. The external diameter of the coil is 814 mm and its height 222 mm. The maximum magnetic flux densities are 5.2 T and 2.5 T respectively in axial and radial directions. The cooling at 20 K is only performed by conduction from a cryocooler to make cryogenics very friendly and transparent for the SMES users. The SMES design and construction are presented as well as the first tests with 10 pancakes. The first cooling down was successful and the thermal system worked as designed. 6 pancakes carry 300 A without any voltage.