The magnetic properties of the SLC intersection region superconducting quadrupole triplets

The measured magnetic-field parameters of the quadrupoles comprising the final triplet lens system for the Stanford Linear Accelerator Center (SLAC) Linear Collider (SLC) intersection region are presented. The minimum design gradient specifications for these quadrupoles are 1.7 T/cm at 4.6 K and 1.6 T/cm at 4.6 K in a 0.6 T external solenoidal field. Superconducting quadrupoles of two lengths have been specified for the SLC triplets. The effective magnetic length of type Q₁ is 66.498+or-0.305 cm and Q₂ is 121.106+or-0.61 cm. The superconducting performance characteristics of the quadrupoles that have been measured are: maximum critical current as a function of bath temperature, as a function of rate of change of magnetic field, and as a percentage of the short sample. Short-sample performance is defined as the current reached by the cable in a perpendicular magnetic field equal to the peak field in the winding at bath temperature. The maximum gradient achieved during testing was 1.04 T/cm (4.25 K) and 2.07 T/cm (3.2 K). This represented 95% of the strand critical current value. The magnetic length of the first Q₂ was measured to be 120.85+or-0.1 cm. The Fourier harmonic coefficients of the magnetic field were measured as a function of current and are reported.