Superconducting Properties of a Prototype Pancake Coil Using a MgB2 Rutherford-Type Stranded Conductor

A prototype pancake coil using a MgB
₂
Rutherford-type stranded conductor for superconducting magnetic energy storage (SMES) proposed in the Advanced Superconducting Power Conditioning System was fabricated and evaluated. The conductor consisted of a CuNi former, eight MgB
₂
wires and four Cu wires, with a twist pitch of 51 mm, and a pancake coil of 200 mm inner diameter, 269 mm outer diameter, and 7 mm thickness was manufactured using the wind-and-react method. The prototype coil was cooled by conduction cooling using refrigerators and the critical current under 1.5 T at 25 K exceeded 700 A. These measurements suggest that several kJ class MgB
₂
SMES using MgB
₂
stranded conductors could be designed appropriately in terms of the bending strain.