Magnetic correction of RHIC triplets

Triplets of large bore quadrupoles will be antisymmetrically placed on either side of all six intersection points of the Relativistic Heavy Ion Collider (RHIC). In RHIC collision optics, the triplets at the two experimental detectors are intended to enable the collision beta function to be reduced to the design goal of β* = 1.0 meter in both planes, in order to minimize the spot size and maximize the luminosity. This requires running with β_max = 1400 meters in the triplet, where the beams will have their largest size, both absolutely and as a fraction of the available aperture. Hence, the ultimate performance of RHIC rests on achieving the highest possible magnetic field quality in the triplets. The authors show the layout of a triplet, with the quadrupoles moved as close together as possible. They list some triplet parameters, such as the different lengths of quadrupoles Q1, Q2, and Q3, and the 5σ beam size - about 71% of the 6.5 cm coil radius. All three quadrupole models have the same coil and iron cross-section in the main body, and all have the same coil saddle ends and electrical lead geometry. Lumped correctors, labeled C1, C2, and C3, carry three nonlinear windings to compensate for measured multipoles, in addition to carrying dipole corrector windings. This paper discusses the correction of magnetic errors expected in the quadrupole bodies and ends, using both these lumped correctors and also quadrupole body tuning shims