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Optics change requests for Run II and possible options for 2015

Optics change requests for Run II and possible options for 2015. S. Fartoukh Many thanks to G. Arduini, B. Dehning, M. Giovannozzi, W. Hofle, M. Lamont, E. Métral , S. Redaelli, R. Tomas, J. Wenninger LBOC 29/04/2015. Just a reminder of some goodies of ATS optics before starting

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Optics change requests for Run II and possible options for 2015

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  1. Optics change requests for Run IIand possible options for 2015 S. Fartoukh Many thanks to G. Arduini, B. Dehning, M. Giovannozzi, W. Hofle, M. Lamont, E. Métral, S. Redaelli, R. Tomas, J. Wenninger LBOC 29/04/2015 Just a reminder of some goodies of ATS optics before starting ... for b* levelling from 5 km to 10 cm (... if we had enough aperture and nothing else to do)

  2. Content • LHC Optics change requests for Run II • Possible options for 2015 • New IR4 optics • Conclusions

  3. LHC Optics change request for Run II For the benefits of a new IR4 optics, both for the profile monitors (WS, BSRT, BGI) and ADT, see G. Trad and G. Kotsian @ LS1-LBOC17

  4. Possible options for 2015 (1/2) • 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 cst phase), even for moderate b* reach. • Option-med: idem as option-min, with New IR4 optics (BGI/BSRT/ADT) with new phase for beam2 compensated by a new IR8-b2 injection optics Eventuallynew IR6 optics (MKD-TCDQ phase) • Option-max: overall new injection and collision optics, and crossing scheme, ATS-compatible  Note that the new IR4 optics is not the same for the med and max options, but leading to similar improvements for the BSRT/BGI/ADT...  New injection, collision and VdM optics following option-max are available under /afs/cern.ch/eng/lhc/optics/ATS_2015  Also available is a new LHC injection optics following Option-med

  5. Possible options for 2015 (2/2)  As soon as a decision is taken, a validation period of a few weeks till 2-3 months should be needed • For tracking studies (dynamic aperture) • Collimation (loss maps) • Failure scenario (in particular new X-scheme in IR8, new MKD-TCT phase) • Collective effects (essentially b-b with new IP1/5 phase advance)  Bad surprises are however very unlikely for any of these 3 options. That is why it would be counter-productive not starting with option-max, and then iterate (or downgrade our ambition) in case ...  The deadline for complete optics production and validation (inc. knobs, X-scheme, squeeze and un-squeeze,...) is Oct-Nov 2014.

  6. New IR4 optics for option-max (1/2) • Beam2 • Beam1 D3.R4 D3.L4 BGI BGI ... The beta’s are also increased at the ADT, and within specification at the BPMC’s

  7. New IR4 optics for option-max (2/2) • Beam2 aperture • Beam1 aperture New n1 (in black) and n1 change (in red) from the nominal to the new optics  When dn1<0, the new n1 is always within MEB specification (n1=7 @ QF and n1=6.7 @ QD)

  8. (Biased) Discussions •  Implementing ATS-compatible optics*)in 2015 has no obvious cons, • both on paper (TBC, the post-LS1 ATS optics proposed being slightly different from the one for HL-LHC already heavily studied), • for commissioning time (based on ATS MD experience in 2011/12) •  Pros are • all the known goodies, in particular flat optics for performance with longer than nominal bunch length, BUT also very large beta*, clean chromatic properties of collision optics including spurious dispersion • the possibilities to maximize here and there the functionalities of ALL insertions • (a priori) no other optics changes requested till LS3 & a demonstration (hopefully!) of one of the main HL-LHC concepts. • *) An “ATS-compatible optics” means an optics with specific phasing properties, which is compatible if needed with a telescopic (un-)squeeze to reach very low (or large) b*at IP1 & 5.

  9. Reserve

  10. New IR4 optics for option-med (1/2) • Beam2 • Beam1 D3.R4 D3.L4 BGI BGI ... The beta’s are also increased at the ADT, and within specification at the BPMC’s

  11. New IR4 optics for option-med(2/2) • B2 aperture @450 GeV • B1 aperture @ 450 GeV New n1 (in black) and n1 change (in red) from the nominal to the new optics  When dn1<0, the new n1 is always within MEB specification (n1=7 @ QF and n1=6.7 @ QD)

  12. New IR8 optics for option-med (1/2)  For the new X-scheme in IR8, see LMC-167  While IR4-b1 can be re-matched at constant phase, the H phase advance of IR4-b2 shall be reduced by Dmx - 0.08 which is then recovered by using IR8  As a result the beam1/2 phase split between IP1 and IP5 changes by the same amount: is there any impact on beam-beam effect?

  13. New IR8 optics for option-med (2/2) IT, Q4.R8& Q5.R8 kept constant  No impact on TL optics matching  No impact on MKI-TDI phase Q4.L8 & Q5.L8 modified but at cst Dmy between MKI and TCLIB

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