MD 3603: Dynamic Aperture with uncorrected dipole b3

The hadron collider options currently investigated as part of the FCC study rely on the use of dipoles with a field strength of 16 T or above in order to achieve the targeted collision energy. From simulations of the current design of these dipoles, a systematic sextupole component of up to factor 10 larger than in the LHC dipoles could be present in these magnets. A similar systematic mispowering of the corrector circuits as is assumed in the LHC may thus have a significantly larger impact on the dynamic aperture and in turn potentially also on the operational performance. During this MD, the dynamic aperture in the presence of large sextupole fields in the LHC at injection energy was measured. By deliberately mispowering the sextupole spool pieces attached to each dipole, a large systematic b3 component is generated and the subsequent change in chromaticity is corrected by the chromaticity sextupoles. Using both the aperture kicker and the AC-dipole as exciters, free and forced dynamic aperture as well as amplitude detuning were measured. Additional linear optics measurements provide insight into the contributions to coupling from the sextupole spool pieces.