Analytical methods to calculate electromagnetic stress of superconducting solenoid magnets.

Compressive magnetic radial stress is favored, over tensile one, for a high field magnet, mainly because it lowers the overall peak magnetic stress within the windings of the magnet. It is of particular importance for a no-insulation (NI) high temperature superconducting (HTS) magnet, because the compressive radial stress leads to good turn-to-turn contact that is essential for current sharing in the NI HTS coils and consequent self-protecting behaviors. Depending on key magnet design parameters such as target center field, background magnetic field, inner and outer winding diameter, and overband radial build, we have shown that electromechanical conditions for a high field superconducting magnet to have compressive radial stress may be analytically pinpointed. With our suggested method, we can identify 3 different patterns of radial turn-to-turn contact behavior in the dry wound coils: (1) fully separated; (2) fully contacted; and (3) mixed (i.e., partially separated and contacted). After that, we suggest an analytical method to calculate stress distributions in dry wound coils by using the electromechanical condition for fully compressive radial stress. Finally, by performing the finite element analysis with examples, we verified that our analytical method shows a good agreement with the numerical one. The results may provide insight for magnet engineers to better overview the electromechanical behaviors of their high field HTS magnets at the early design stage. [ABSTRACT FROM AUTHOR]