Conceptual design of the orbit correctors for D2 and Q4

In the luminosity upgrade of the Large Hadron Collider, many dipole, quadrupole, and corrector magnets around the ATLAS and CMS detectors are replaced with larger aperture magnets. The purpose is to reduce the beam size at the interaction point by a factor of two and thus to increase the number of particle collisions. This article presents the results of a preliminary design study of the replacements for double-aperture orbit corrector magnets positioned next to the first matching section quadrupole Q4 and the new correctors to be placed next to the recombination dipole D2. The apertures of the correctors are increased from the current 70 mm diameter to 105 mm. The larger apertures and the fixed 188/194 mm distance between the beams pose design challenges due to magnetic coupling between the apertures. The design proposal described in this report consists of a two-in-one Nb-Ti magnet with one aperture providing horizontal and the other vertical correction. The magnetic forces are taken primarily by stainless steel collars with possibly further support from the rigid iron yoke. The design of the yoke is essential in shielding the two apertures from each other.