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Optics options for the 2015 run

Optics options for the 2015 run. Massimo Giovannozzi Possible optics configurations Few additional points Current status of validation activities Next steps

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Optics options for the 2015 run

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  1. Optics options for the 2015 run Massimo Giovannozzi • Possible optics configurations • Few additional points • Current status of validation activities • Next steps Acknowledgements: G. Arduini, R. Bruce, H. Burkhardt, B. Dehning, S. Fartoukh, B. Gorini, W. Höfle, J. Jowett, M. Lamont, R. de Maria, E. Meschi, D. Mirarchi, S. Redaelli, T. Risselada, R. Tomas, J. Wenninger. M. Giovannozzi – 2014 Chamonix Workshop

  2. Possible optics configurations - I • Possible criteria to define different configurations • To incorporate the lessons learnt from Run I • To increase the performance reach • To prepare for the future • Another element might be taken into account: • The LHC has undergone heavy activities during LS1. To keep the optics unchanged might have some advantage. • Important remark: • The different configurations provide the same values of b* at the experimental points as needed (see R. Bruce talk). M. Giovannozzi – 2014 Chamonix Workshop

  3. Possible optics configurations - II S. Fartoukh, LMC 179 M. Giovannozzi – 2014 Chamonix Workshop

  4. Possible optics configurations - III Indeed, the new IR4 optics will be beneficial also other profile monitors (WS, BSRT, BGI) and transverse damper (ADT) S. Fartoukh, LMC 179 M. Giovannozzi – 2014 Chamonix Workshop

  5. Possible optics configurations - IV • Option-min: no optics change w.r.t. 2012 unless absolutely necessary (25 ns, 6.5 TeV vs. 4 TeV) • New Xing scheme in IR1/5 (MCBX) and IR8 (see LMC-167) • New IR2 squeeze sequence and collision optics (at constant phase). • Option-med: idem as option-min, with • New IR4 optics with new phase for Beam 2 compensated by a new IR8-Beam 2 injection optics. The Beam1/2 phase split between IP1 and IP5 changes: is there any impact on beam-beam effect? • Possibly, new IR6 optics (MKD-TCDQ phase) • Option-max: overall new injection and collision optics, and crossing scheme, ATS-compatible* • The new IR4 optics is not the same for the med and max options, but leads to similar improvements for instrumentation and damper. *An ATS-compatible optics has specific phasing properties compatible with a telescopic (un-)squeeze to reach very low (or large) b* at IP1 and 5. S. Fartoukh, LMC 179 M. Giovannozzi – 2014 Chamonix Workshop

  6. New IR4 optics for option-max • Beam2 • Beam1 D3.R4 D3.L4 BGI BGI S. Fartoukh, LMC 179 M. Giovannozzi – 2014 Chamonix Workshop

  7. Pickups for ADT after LS1 New pick-up layout and new optics W. Hofle, G. Kotzian, D. Valuch LBOC M. Giovannozzi – 2014 Chamonix Workshop

  8. Estimated improvements for ADT • Design peak kick strength is 2 mradat 450 GeV/c (assuming b=100 m). • For Run I the effect on beam is factor 1.6 higher for H.B1, V.B1, H.B2, and 1.8 higher for V.B2 (because b’s much higher than 100 m) • For Run II, the new optics brings further improvement for all beams and planes W. Hofle, G. Kotzian, D. Valuch LBOC M. Giovannozzi – 2014 Chamonix Workshop

  9. Estimated beam sizes at instruments - I Minimum beam sizes for option-min G. Trad LBOC M. Giovannozzi – 2014 Chamonix Workshop

  10. Estimated beam sizes at instruments - II Optics improvements Beam 1 Beam 2 G. Trad LBOC M. Giovannozzi – 2014 Chamonix Workshop

  11. Possible optics configurations - V • Option-max • Incorporates the lessons learnt from Run I • Tested with pilots during machine studies • Implement the changes to improve instrumentation and transverse damper. • Increases the performance reach • Flat optics for use with longer than nominal bunch length • Very large b* • Clean chromatic properties of collision optics including spurious dispersion • Prepares for the future • It is the baseline of HL-LHC. M. Giovannozzi – 2014 Chamonix Workshop

  12. Few additional points - I • Some specific points to consider (independently of the actual optics option selected): • Fractional tune control: • Currently the change of phase advance of IR1 and 5 determines the transition from injection to collision tune. • The tune change occurs at the first point in the squeeze. • Some observations from Run I: the change of quadrupoles’ strength induces beam losses due to orbit effects. • Possible mitigation measure: to stretch the duration of the tune transition stage, but the squeeze would take more time. • Proposal: • The IR1 and 5 optics with collision tune should be used since injection. • The tune should be controlled with the MQTs. • This would provide the flexibility of • Controlling the fractional tune value at injection • Controlling the timing and the duration of the tune change M. Giovannozzi – 2014 Chamonix Workshop

  13. Few additional points - II • Special runs: • LHCf: typical b* values in the range 11-20 m • Van der Meer scans: • ATLAS, CMS: typical b* values around 20 m • LHCb: 30-40 m • High-beta: 90 m • Standard approach: • Starting from nominal injection un-squeeze b* • For LHCf, or Van der Meer • For High-beta M. Giovannozzi – 2014 Chamonix Workshop

  14. Few additional points - III • Possible synergies: • Common un-squeeze till 20 m • Simplifies commissioning. • Leaves unchanged un-squeeze time. • Increase b* values at injection • Reduces un-squeeze times. • Requires re-commissioning injection. • Possible only for IR1/5. • Worthwhile only if high-beta run is longer than two weeks M. Giovannozzi – 2014 Chamonix Workshop

  15. Few additional points - IV • Triplets’ strength in collision for point 2 and 8: • Injection constraints impose to run the triplets at around 220 T/m in IR2 and 8. • The triplets’ circuit rating imposes to reduce the strength of the quadrupoles at beam energies higher than 6.78 TeV. Hence, ramp and squeeze is imposed in IR2 and 8 if Ebeam > 6.78 TeV. • Furthermore, beams can be put in collision only if the triplets’ gradient is reduced to the nominal value of 205 T/m. • This implies the need of one of the two options: • Performing a pre-squeeze, i.e., reducing the triplets’ strength at constant b*. • Reduce the triplets’ strength during the squeeze. • The luminosity in IR2 and 8 might allow to obtain a derogation to the rule of reducing the triplets’ strength before putting the beams in collision: MP3 should make an official statement on this point. • If accepted, this new configuration would simplify the optics changes at least below 6.78 TeV. M. Giovannozzi – 2014 Chamonix Workshop

  16. Current status of validation activities - I • Starting point: comparison between option-min and option-max • DA studies (with and w/o beam-beam effects): no major differences found between the two configurations. • Multipole imperfections: as-built machine (with 60 seeds) • Octupoles • Injection: -10/-5/0/5/10 A • Collision: -570/0/570 A • Beam-beam • LR effects in all IRs (injection and collision) • Head-on collision at IP1/5/8 (DQbb~0.01) S. Fartoukh, LMC 188 M. Giovannozzi – 2014 Chamonix Workshop

  17. Current status of validation activities - II • New crossing scheme in IR8: no show stoppers found. The aperture at injection is enough even for failure scenarios. • Cleaning efficiency: differences found. • Machine protection: for Beam 2 the phase advance between dump kicker and TCT is essentially the worse possible. • The LMC decided that the understanding of the cleaning should be pursued with beam in 2015 and that the initial optics configuration will not be option-max. • The validation activities should move to option-med. J. Uythoven, LMC 188 R. Bruce, LMC 188 M. Giovannozzi – 2014 Chamonix Workshop

  18. Next steps - I • Optics validation • Option-med should be studied • Performance in terms of DA. It is closer to option-min and no surprises are expected. • Performance in terms of cleaning efficiency. It should be assessed. • Optics preparation • Define a strategy for dealing with the generic additional points mentioned earlier. • Prepare optics database for • Validation studies of option-intermediate • Settings generation for optics selected for 2015 run • NB: IR1/2/3/5/6/7 have the same optics for option-min and option-med. Results to be presented at the LMC M. Giovannozzi – 2014 Chamonix Workshop

  19. Next steps - II • Option-max • Even if it will not be the optics configuration for 2015, it should not be left in the current status till beam tests in 2015. • Additional studies should be performed to understand better the cleaning efficiency and, possibly, find mitigation measures. • Plans for beam studies in 2015 should be prepared and, based on results, milestones for implementation as operational optics should be worked out. M. Giovannozzi – 2014 Chamonix Workshop

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