Linear optics - I Low beta* at injection –Reduction of injection could potentially reduce time to collisions and allow for a more relaxed ramp&squeeze, leading to gains in integrated luminosity Is it really worth it? Reduced / Flat optics at top energy –Feasibility of 30cm beta* or flat optics at top energy. Round optics really worth it (ATS is the future)? Maybe better to focus on flat optics. High Beta (~2km) –Should be operational time but some aspects might need verification in MD Half integer tunes –Largest resonance free area in tune space. Still an option for HL-LHC and future colliders, but off-momentum behaviour in LHC not studied/understood. 18/01/2016LHC Studies WG - MG1

Linear optics - II Linear coupling... –The use of the DOROS system to measure and correct the linear coupling. Could we try to use it during the ramp and squeeze? –How would we bench mark the measurements? Also use it to measure the phase close to the IPs to see if we can have higher accuracy on the local corrections. 18/01/2016LHC Studies WG - MG2

Non-linear optics - I b3 and Q’ –long-standing issue of Q' discrepancy. Studies in 2015 suggested DQ' from shifts in MCO powering is correct within 10%, but other potential sources have never really been studied in detail. –Measurement of natural chromaticity –Checks of b3 correction with MCS b4, b5 and non-linear chromaticities Checks of locality of b5 corrections at injection and MCDO behaviour Several aspects of the behaviour of the MCDO in 2015 are not understood. In particular the effect of the MCD on Q'' and MCO on Q'''. Measurement of feed-down from MCO trims may indicate if there is a systematic mis-alignment of the nested MCDO. Measurements of the chromatic detuning will also provide for free measurements of the RDTs Nonlinear chromaticity/detuning with amplitude at top energy 18/01/2016LHC Studies WG - MG3

Non-linear optics - II Nonlinear errors in experimental insertions –Correction of understood errors: To be done in commissioning Studies of the nonlinear errors in the IRs at 40cm –About half of the relevant nonlinear multipoles in IR1 and IR5 have either not yet been studied or show significant discrepancies with respect to the magnetic model. Use of additional methods, such as RDT measurements, and a wider variety of closed orbit bumps for feed-down studies should provide additional constraints to help understand discrepancies of nonlinear multipoles. IR-nonlinear errors with alternative optics –Different configurations, for example 30cm beta* or flat optics, could provide additional constraints on sources of discrepancy with magnetic model. –Single IP squeeze for IR nonlinear errors: Performing squeeze of a single IRs would eliminate this complication allowing a local correction. This would require considerable preparation, but has synergy with beam-beam-wire-compensation studies. 18/01/2016LHC Studies WG - MG4

Non-linear optics - III Nonlinear coupling –High amplitude kicks for different settings of the linear coupling. Changing the polarity of one of the defocusing octupoles in order to see if this reduces the nonlinear delta q min. At which energy? 18/01/2016LHC Studies WG - MG5

DA studies - I DA at injection: There are several aspects of the DA we would like to study further. The aims of these three points can in general overlap. Kicked beam studies will also provide data for RDTs –Models predict significant reductions in DA, and large increase in 2nd order detuning, at injection with MO strengths employed in We can check these predictions with Beam. Not high priority… –Two beam-based methods to study DA have been employed in Run 1. Both show a good agreement with their respective models, but neither has been compared directly to the other. We could analyse existing data before asking for MD time Measurements of DA off-momentum hinted at a significant reduction of the dynamic aperture off-momentum. These were coincidental observations only. –Relevant knowing that the future is ATS with better chromatic properties? 18/01/2016LHC Studies WG - MG6

DA studies - II AC-dipole DA: Recent work has began to explore the concept of dynamic aperture for beams undergoing driven oscillations forced by an AC-dipole. These studies should be complemented by beam-based studies. Better understanding of the DA for driven oscillations could potentially improve the efficiency of optics measurements and provide an additional tool for us to study the nonlinear dynamics. –Interesting topic: paper studies should be performed before MD time requested? 18/01/2016LHC Studies WG - MG7

DA studies - III Dynamic aperture at top energy Higher order errors are difficult to study via feed-down and detuning. DA provides a possible observable. Measurement via heating of the beam with ADT should be viable at top energy and has been demonstrated at injection. Such techniques should be demonstrated at top energy. Once demonstrated this method could be used to validate IR corrections for lower orders determined from other observables, and could be used to determine corrections for higher orders - for example b6. 18/01/2016LHC Studies WG - MG8