Speaker
Description
SPARC is a compact, high-field tokamak based on high temperature superconductor (HTS) magnets developed by Commonwealth Fusion Systems and the Massachusetts Institute of Technology. This research explores the mechanical and electromagnetic behavior of SPARC’s cable-based magnet systems, namely the Central Solenoid (CS), the Poloidal Field Coils (PF), and the feeder (FEED) systems. Our studies focus on the CS, which will experience an average hoop compression of 350 MPa from the bucking Toroidal Field (TF) magnets. We present the design and execution of two experiments which systematically subject the superconductor to operation-relevant loads and monitor the reversible and irreversible effects on Ic at 77 K. The first experiment explores the cable’s limits under static and cyclic transverse (SPARC radial) loading alone. We find that the cable unit cell is able to withstand 100s of cycles without degradation at 400 MPa of transverse compression—and that the onset of permanent degradation is not observed until >550 MPa. The second experiment explores a combined longitudinal (along cable-axis) and transverse compression, which are both present during hoop compression observed in the CS. To that end we developed a test rig which is able to cyclically load cable samples longitudinally and transversely (simultaneously), in liquid nitrogen, with loads up to 533kN (1.2 GPa) longitudinally (without buckling the cables) and 850kN (535 MPa) in transverse compression—while at the same time allowing for in-situ transport current measurements.
