Prospects for beam-based study of dodecapole nonlinearities in the CERN High-Luminosity Large Hadron Collider

Nonlinear magnetic errors in low-β insertions can have a significant impact on the beam-dynamics of a collider such as the CERN Large Hadron Collider (LHC) and its luminosity upgrade (HL-LHC). Indeed, correction of sextupole and octupole magnetic errors in LHC experimental insertions has yielded clear operational benefits in recent years. Numerous studies predict however, that even correction of more obstreperous nonlinearitites (up to dodecapole order) will be required to ensure successful exploitation of the HL-LHC. During HL-LHC design, it was envisaged that compensation of high-order nonlinearities would be based upon optimal correction of specific nonlinear resonances determined from magnetic measurement during construction. Experience at the LHC however, demonstrated that beam-based measurement and correction of the sextupole and octupole errors was an essential complement to this strategy. As such, significant interest also exists regarding the practicality of beam-based observables of multipoles up to dodecapole order. Based on experience during the LHC’s second operational run, the viability of beam-based observables relevant to dodecapole order errors in the experimental insertions of the HL-LHC are assessed and discussed in detail in this paper.