Report from LHC MD 1391: First tests of the variation of amplitude detuning with crossing angle as an observable for high-order errors in low-β∗ colliders

Nonlinear errors in experimental insertions can pose a significant challenge to the operability of low-β∗ colliders. When crossing schemes are applied high-order errors, such as decapole and dodecapole multipole components in triplets and separation dipoles, can feed-down to give a normal octupole perturbation. Such fields may contribute to distortion of the assumed tune footprint, influencing lifetime and the Landau damping of instabilities. Conversely, comparison of amplitude detuning coefficients with and without crossing schemes applied should allow for the beam-based study of such high-order errors. In this note first measurements of amplitude detuning with crossing bumps in the experimental insertions are reported.