Stress management in high-field dipoles

The management of Lorentz stress and preload forces is the biggest single challenge in the effort to develop collider dipoles with ever greater field strength. Were the Lorentz forces permitted to accumulate through a coil, they would exceed the limit for strain degradation for the A15 and high-temperature superconductors which are capable of sustaining such field strength. A strategy has been devised for intercepting Lorentz stress within the coil to overcome this problem in high-field block-coil dipoles. The coil is fabricated in multiple independent shells, in which a high-strength structure and a soft-modulus spring are used to bypass stress between succeeding layers. Finite-element analysis and experimental studies have demonstrated that this strategy can limit the maximum stress anywhere in a coil so that it nowhere exceeds strain degradation limits for fields at least to 20 Tesla.