Large aperture quadrupoles for RHIC interaction regions

Abstract

The ultimate luminosity performance of the Relativistic Heavy Ion Collider (RHIC) depends on the field quality in the large aperture (130 mm) superconducting quadrupoles in the interaction regions1i2. In this paper we discuss the design features that are incorporated to obtain a good field quality. Coil midplane gap and pole shims may be adjusted to remove certain field harmonics due to systematic errors in construction. Iron tuning shims will be inserted at eight strategic locations in the assembled magnets to correct the measured values of harmonics in each magnet. The performance of two prototype magnets and upgrades under consideration will be discussed.

Tuning shims for high field quality in superconducting magnets

“…The Relativistic Heavy Ion Collider [I], [2] being built at Brookhaven National Laboratory (BNL) has six interaction ture quadrupoles [3] in four focusing triplets. In order to achieve a high luminosity, the beam will be squeezed to the smallest possible size @'=I meter) in two interaction regions.…”

“…The magnetic length of the three interaction region quadrupoles in the focusing triplet are 1.44 m, 3.4 m and 2.1 m. They all have the same cross section. The detailed design of these magnets is described elsewhere [3].…”

Improving the design and analysis of superconducting magnets for particle accelerators

“…As mentioned earlier, in order to simplify construction and to save the cost of tooling, the RHIC arc quadrupoles [160] and RHIC insertions quadrupoles [69] are collared like dipoles. This creates an elliptical deformation of the yoke aperture which breaks the quadrupole symmetry and therefore generates the non-allowed octupole harmonic b3 (also b7, b,,, etc.).…”

Removal of axial twist in RHIC insertion quadrupole magnets

“…The 13cm quadrupole helium containment vessel includes a two piece stainless steel shell, 6.35mm thick, with longitudinal seams at the twelve and six o'clock locations [1]. The shells of all twelve 13cm quadrupole units installed in Sextant #5 (comprising the first sextant test in January, 1997) have been manually seam welded at BNL using TIG welding equipment and a procedure which calls for two welders operating simultaneously on either side (the cold mass is rotated 90 deg.…”