Experiment of HTS stress-balanced helical coil

High Temperature Superconductors (HTS) are expected to improve small size S uperconducting Magnetic Energy Storage (SMES) systems, However, they are ex tremely brittle and require special structural considerations to limit tens ile stresses. We propose the concept of Stress-Balanced Coil (SBC) applied to SMES with large aspect ratio (= major radius / minor radius) coil. The S EC is a helical-winding torus coil which balances magnetic pressures at the coil nose part where the magnetic field strength reaches its maximum value . The SEC can reduce coil stresses and thus it can be applied to SMES with HTS conductors. In order to show the effect of the SEC, we designed and fab ricated a small experimental coil by using 400 m of Ag-sheathed Bi-2223 sup erconducting tape.