Nonlinear optics commissioning in the LHC

So far, the LHC has operated without any dedicated commissioning of the nonlinear optics at top energy. As is reduced however, the impact of nonlinear errors in experimental insertions may become sizable. Below , and in particular with possible LHC con gurations approaching , an operational impact from uncompen-sated nonlinear errors in the IRs is to be expected. Notably the contribution of normal octupole errors in IR1 and IR5 to the tune footprint becomes comparable to that created by the Landau octupoles, with implications for the performance of instrumentation and Landau damping of in-stabilities. In the HL-LHC compensation of IR-nonlinear sources may become a critical issue, with feed-down from IR-sextupole errors having the potential to generate substantial linear optics perturbations. This effect will require an evolution of the linear optics commissioning strategy in the LHC and HL-LHC. Current understanding of the impact of these errors and our ability to correct them will be reported. Nonlinear optics commissioning activities under-taken elsewhere in the machine cycle will also be introduced.