Fig. 2. Nb3Sn bounds of superconductivity
While fabrication advancements have led to the optimisation of NbTi
cabling [27], the fundamental design has not changed since it’s
creation at the Rutherford Appleton Laboratory [36, 51]. The
Rutherford cable is the most widely used cable type in accelerator
magnets [26, 51]. A Rutherford cable is composed of fully transposed
twisted composite strands, shown below in Figure 3 [34]. The cable
critical current Ic is normally the sum of each strand’s
critical current [53]. The Rutherford cable is still used today
because it is permeable to liquid coolants due to its braided structure
and the two layers of fully transposed strands limit nonuniform current
distribution within the cable, caused by the cables self field and the
flux linkage between strands [51]. There are three highly stressed
sections of a Rutherford cabled pulsed solenoid, the copper wire matrix
around the filaments, the epoxy reinforcement and the cable (or core
strip) midplane. [8, 23, 46]