Corrections of Systematic Normal Decapole Field Errors in the HL-LHC Separation/Recombination Dipoles

Magnetic measurements revealed that the new normal decapole ($b_5$) errors of the recombination dipoles (D2) for the HL-LHC could have a systematic component of up to 11 units. Based on previous studies, it was predicted that the current corrections would not be able to compensate this, thereby leading to a degradation of the dynamic aperture. On the other hand, the separation dipole D1 is expected to have a systematic $b_5$ component of 6 units to 7 units and its contribution to the resonance driving terms will partly compensate the effect of D2, due to the opposite field strength of the main component. Simulations were performed to address these concerns and to verify the compensation assumption, yet confirmed that the errors could only be partly compensated. In addition, various normal decapole resonance driving terms were examined as correction targets and the dependence of feed-down to amplitude detuning on this choice was discovered.