1. LHC Technical Committee, 23/05/20071 LHC Commissioning Phases Squeeze presented by Massimo Giovannozzi on behalf of the LHCCWG Particular thanks to S. Redaelli, G. Arduini, R. Assmann, R. Bailey, B. Goddard, V. Kain, M. Lamont, L. Ponce, J. Wenninger, EICs, LHCCWG members and ABP-LCU members

2. LHC Technical Committee, 23/05/20072 LHC Commissioning Phase 11 – Squeeze Phase A.11: Squeeze – Objectives – Entry conditions – Commissioning procedures – Exit conditions Summary

3. LHC Technical Committee, 23/05/20073 Squeeze - General considerations Physics runs with un-squeezed beams imply that the squeeze is only needed after: Required Machine Protection in place Better understanding of the collimation system Stable separated beams at 7 TeV Can bring beams into collision Can master the ramp and get interleaved beams to 7 TeV A fairly good knowledge of the LHC will have been gained by the time when we will try the squeeze. First turn Circulating beam 450 GeV: initial 450 GeV: detailed 450 GeV: increasing intensity Two-beam operation Snap-back Ramp Single-beam 7 TeV Two-beam 7 Tev Collisions Squeeze Snap-back Ramp Single-beam 7 TeV Adapted from M. Lamont

4. LHC Technical Committee, 23/05/20074 LHC Stage A: Commissioning phases PhaseDescription A.1Injection and first turn: injection commissioning; threading, commissioning beam instrumentation. A.2Circulating pilot: establish circulating beam, closed orbit, tunes, RF capture A.3450 GeV initial commissioning: initial commissioning of beam instrumentation, beam dump A.4450 GeV optics: beta beating, dispersion, coupling, non-linear field quality, aperture A.5450 GeV, Increasing intensity: prepare the LHC for unsafe beam A.6450 GeV, two beam operation A.7450 GeV, collisions A.8Snap-back and ramp: single beam A.9Top energy checks A.10Top energy, collisions A.11Squeeze: commissioning the betatron squeeze in all IP's A.12Physics runs: physics with partially squeezed beams, no crossing in IP1 and IP5 Phases for full commissioning Stage A (pilot physics run) Basic Objectives: Master mechanics of squeeze Control and protect aperture during optics change Control orbit and optics during squeeze Establish procedures and references (orbit, tune) for the feedback operation Establish collimators settings during the squeeze (in particular TCTs to protect the triplet) as well as TCDQ Prepare for collisions with squeezed beams and physics

5. LHC Technical Committee, 23/05/20075 Squeeze – Overview of Steps Involved StepActivityPriority A.11.1 Beam-based calibration of collimators for triplet protection and cleaning Collimation Team 1 A.11.2Load magnet settings into the hardwareABP/OP/PO1 A.11.3 Running the betatron squeeze with detailed measurements (beam parameters, optics,...) for new beta* ABP/OP1 A.11.4Preparation to bring the beams into collisionABP/OP1 Priority categories (71th LTC): 1.absolutely mandatory, 2.should be done if possible, 3.would be nice if it could be done Iterative procedure for steps 1 to 3: to be repeated for each intermediate beta* stop point until we can get to the final value for physics. Remark: The squeeze will be performed by changing gradients (linear interpolation) in between two matched optics. Recap of key parameters: Max 156 bunches No crossing angle beta* = 2 m

6. LHC Technical Committee, 23/05/20076 Squeeze - General commissioning approach Goal: commission simultaneous squeeze of the IP1 and IP5, both beams How can we get there during commissioning? 1. Start with a single pilot Beam 1 and squeeze IP1 without separation 2. Verify squeeze of one beam with parallel separation 3. Squeeze two separated pilot beams in IP1 4. Commission squeeze in IP5 with a single pilot Beam 1 (squeeze in 2 IP’s in parallel) - try with separation on 5. Try two beams in IP5 as well Remark: First commissioning done with detector magnets ON (input from their effect from collisions without squeeze, A.10). We should be ready to switch them OFF in case of difficulties. Remark: Squeeze of IP8 (and IP2) will follow in a similar manner.

7. LHC Technical Committee, 23/05/20077 Squeeze – Entry Conditions - I Assumption: The squeeze takes place with circulating beams at 7 TeV and does not start at lower energies. Beams separated, no crossing in IP1 and IP5 (works up to 156 on 156) Stable and well measured optics at 7 TeV for both - separated – beams (as exit of A.9): – Reference "golden" orbit with beam-beam separation ON established for feedback. – Reference "golden" orbit established in the cleaning and dump insertions. – Beta-beating measured and under control in all the machine. Orbit and optics stable in the cleaning and dump insertions (1 sigma at 7 TeV). – If needed, the orbit feedback must be commissioned and operational, at least for local orbit control at collimator locations (IR7 and IR6, maybe also IR3 if momentum cleaning is needed). Aperture measured at critical bottlenecks and corrected to acceptable levels (as exit of A.4 and A.9). Aperture bottlenecks will appear during betatron squeeze: special measurements to be performed at 450 GeV. Tolerance tables on beam parameters to be defined…

8. LHC Technical Committee, 23/05/20078 Squeeze – Entry Conditions - II Collimators and dump protection elements (TCDQ) tuned to ensure required cleaning and protection. – Cleaning collimators: after-ramp settings of injection optics at 7 TeV. – Dump system fully commissioned for 7 TeV beams. NB: collimators and dump protection elements (TCDQ) will require setting adjustments for every beta* step. Tertiary collimators (TCTs) hardware-commissioned and ready to move. Beam-based determination of closed orbit, beam size and divergence at each TCTs. Landau octupole circuits fully hardware-commissioned. Ready-to-use magnet settings from MADX optics files and all timing tables (trigger events/measurements). Full commissioning of squeeze settings generation and trim (timing tables) for insertion magnets. A decision must be taken beforehand on the number of steps during the squeeze and on the final value of beta* for physics at each IP.

9. LHC Technical Committee, 23/05/20079 Squeeze – Entry Conditions - III All instrumentation operational (no special requirements for squeeze). Instrumentation commissioning done at phases A.3, A.6, A.10. Continuous emittance/beam size measurement extremely useful. All software operational (no special requirements for squeeze). Orbit monitoring + feedback available (commissioned for constant optics). Q, Q' monitoring + feedback available (commissioned for constant optics). Need dedicated commissioning for feedback! Change of optics matrices for correction algorithm, triggered from sequencer or manual timing distribution, has to be operational. However, the algorithm proved to converge also with 100% beta-beating… Distribution of beta squeeze factor for machine protection commissioned. Roman Pots, VELO, LHCf OUT. Verification of the interlock signals. Detector magnets ON

10. LHC Technical Committee, 23/05/200710 Squeeze – Stage A.11.1 – Setup of TCTs for triplet protection and cleaning - I Collimators settings based on measured apertures (phases A.4, A.9). End-of-ramp settings for the collimators can be kept up to beta* ~ 6 m. Then, TCT will be set such that the triplet aperture is protected for the next beta* value. All the other collimators and TCDQ will be moved in to provide cleaning and protection for reduced aperture corresponding to next beta* value. T. Weiler Collimation WG#85 Remarks: TCTs will always be used to ensure triplets protection (independently on intensity/beta* values).

11. LHC Technical Committee, 23/05/200711 Squeeze – Stage A.11.1 – Setup of TCTs for triplet protection and cleaning - II R. Assmann LHCCWG#18

12. LHC Technical Committee, 23/05/200712 Squeeze – Stage A.11.1 – Setup of TCTs for triplet protection and cleaning - III R. Assmann LHCCWG#18 Performed with TCP initially

13. LHC Technical Committee, 23/05/200713 Squeeze – Stage A.11.2 – Load settings - I Load the relevant functions of current versus time in the hardware, namely Insertion quadrupoles Lattice sextupoles to correct chromaticity during squeeze Insertion correctors M. Lamont LHCCWG#18 Remark: the target for Stage A is beta* = 2 m. Nonlinear correctors in triplets are not needed above beta* = 1 m. Otherwise functions for these circuits should be loaded, too.

14. LHC Technical Committee, 23/05/200714 - As many functions as the foreseen beta* steps have to be generated. - Need to define the appropriate timing events for each step. -Functions loaded ~ 10 s before the squeeze, then triggered by timing events. -Few minutes are needed to generate the settings on-line (including matrices for feedback). Squeeze – Stage A.11.2 – Load settings - II M. Lamont LHCCWG#18 Do one beam at a time, one IP at a time according to the pre-defined order. Obviously this will not be the case for standard operation but we should start simple. dI/dt limits: Q4 is usually the limiting circuit for the squeeze  t for each beta* step: max of  t for each insertion quadrupole circuit.

15. LHC Technical Committee, 23/05/200715 Squeeze – Stage A.11.3 – Run the squeeze - I Once functions for the first beta* step are loaded and ready in the hardware, the squeeze can be triggered by timing events sent out by the operators. Before this… 1.Switch ON continuous monitoring of tune and chromaticity (BBQ, PLL). 2.Monitor beam losses around the ring, in particular in the IP and in the cleaning IR's. 3.Continuous monitoring of the orbit. Feedback working (cleaning insertions, dump region AND IP that is being squeezed). 4.If it is available, start a monitoring of the local orbit at the TCTs (H + V). Save data for later analysis. Then… 1.Trigger the change to the first beta* value by sending the appropriate timing event. 2.Ready to dump if something goes wrong.

16. LHC Technical Committee, 23/05/200716 Squeeze – Stage A.11.3 – Run the squeeze - II In case everything goes well… 1.Perform the required measurements (optics, aperture,...) at the new beta* value. Detailed measurement program and its procedures to be defined. Define appropriate check procedures for optics and orbit in collimation and dump regions. 2.If necessary, adjust beta* with optics knobs (MADX on-line model). 3.Check losses and beam halo / adjust cleaning collimators and TCDQ for next step, if needed (changes only required for beta*< ~ 6 m). 4.Set the tertiary collimators to ensure an adequate level of MQX protection (later, with higher intensities, also to ensure cleaning!). 5.Record optimum collimator settings in the appropriated databases for the generation of the time functions of settings.

17. LHC Technical Committee, 23/05/200717 Squeeze – Stage A.11.3 – Run the squeeze - III Ready to move to the next beta* value. 1. Load functions for new beta* step for the insertion magnets. 2. Load updated settings for the main sextupole families. 3. Update the octupole settings if needed (depends on collimator settings/transverse feedback). Trigger the next beta* step. In case something goes wrong and the beam is dumped, try to understand where is the problem (post mortem analysis) and restart.

18. LHC Technical Committee, 23/05/200718 Squeeze – Stage A.11.3 – Run the squeeze on paper - I

19. LHC Technical Committee, 23/05/200719 Squeeze – Stage A.11.3 – Run the squeeze on paper - II

20. LHC Technical Committee, 23/05/200720 Squeeze – Stage A.11.3 – Run the squeeze on paper - III LHCCWG#18 Simulations performed on a perfect machine…

21. LHC Technical Committee, 23/05/200721 Squeeze – Stage A.11.3 – Run the squeeze on paper - IV LHCCWG#18 Simulations performed on a perfect machine…

22. LHC Technical Committee, 23/05/200722 Squeeze – Stage A.11.3 – Run the squeeze on paper - IV LHCCWG#18 Simulations performed on a perfect machine…

23. LHC Technical Committee, 23/05/200723 Squeeze – Stage A.11.3 – Run the squeeze with real magnets - I W. Venturini LHCCWG#21

24. LHC Technical Committee, 23/05/200724 Squeeze – Stage A.11.3 – Run the squeeze with real magnets - II W. Venturini LHCCWG#21

25. LHC Technical Committee, 23/05/200725 Squeeze – Stage A.11.3 – Run the squeeze with real magnets - III W. Venturini LHCCWG#21

26. LHC Technical Committee, 23/05/200726 Squeeze – Stage A.11.3 – Run the squeeze with real magnets - IV W. Venturini LHCCWG#21

27. LHC Technical Committee, 23/05/200727 Squeeze – Stage A.11.4 – Preparation to bring the beams into collision Assume that we are able to squeeze both beams separately for beta* values down to the value agreed for physics runs. Settings for movable devices are also defined. Then, after this (details in A.10): Inject both beams, ramp and squeeze them both (with separation still ON). Once both beams are squeezed, load into the power supplies of the orbit correctors the functions to set the separation OFF (get them from MADX model). Switch OFF the orbit feedback (local orbit correction at the IR(s) that is(are) being squeezed) and trigger the event "go in collision“ (next phase…).

28. LHC Technical Committee, 23/05/200728 Squeeze – Exit Conditions Betatron squeeze commissioned in all relevant IPs in a defined number of step points. – Goal: define the maximum amount of losses and the required beam quality (emittance blow-up, final beta* value) after squeeze. Definition of time-dependent settings for all the movable devices (collimators and TCDQ) versus beta* values and versus beam-beam separation, to be used later for automatic squeeze triggered by sequencer. This includes also interlocks position functions. Definition of reference orbits in the experimental insertions versus beta*. Definition of procedures for feedback operation – reference orbit – when to switch it on/off Definition of procedures for Q, Q' feedback operation. Definition of procedures for using Landau octupoles (expected to be needed only for higher beam intensities).

29. LHC Technical Committee, 23/05/200729 Summary Phase A.11 : – Squeeze beams Main focus is on: – Control the mechanics of the squeeze – Control and protect the aperture during the squeeze – Control the orbit and the optics during the squeeze – Protection of triplets using TCTs – Define the actual procedure/sequence to squeeze the various insertions At the end of this phase: - beams can be brought in collision…

30. LHC Technical Committee, 23/05/200730 References Web documentation LHC Commissioning proceduresLHC Commissioning procedures: Phase A.11[S. Redaelli] Papers: Squeeze criteria & requirements – Chamonix XIV[O. Brüning] What is required to safely get the beam out of the LHC – Chamonix XV[B. Goddard] Beam commissioning of the collimation system – Chamonix XV [R. Assmann] LHCCWG presentations: Collimation During Ramp and Squeeze, LHCCWG#18[R. Assmann] Squeeze mechanicsSqueeze mechanics, LHCCWG#18[M. Lamont] Squeeze optics and power converter settings, LHCCWG#18 [S. Fartoukh, M. Giovannozzi, J. Jowett, Y. Papaphilippou] Commissioning Procedures, LHCCWG#21[S. Redaelli] 450 GeV Optics: IR Aperture and IR Bumps450 GeV Optics: IR Aperture and IR Bumps, LHCCWG#13 [Y. Papaphilippou] 450 GeV Optics – Mechanical Aperture and Momentum Aperture450 GeV Optics – Mechanical Aperture and Momentum Aperture, LHCCWG#11[S. Redaelli], Overview of Feedbacks and Implications for CommissioningOverview of Feedbacks and Implications for Commissioning, LHCCWG#6[R. Steinhagen] Response Matrix Measurements and AnalysisResponse Matrix Measurements and Analysis, LHCCWG#9[J. Wenninger] Behaviour of the magnets through the squeezeBehaviour of the magnets through the squeeze, LHCCWG#21[W. Venturini] Optics measurements needed at top energy, LHCCWG#22 [F. Zimmermann] Two-beam operation, LHCCWG#25 [R. Assmann] Other presentations: IR1 & IR5 optics updated for the LHC V6.5, LTC 31/03/2004[S. Fartoukh] V6.5 optics development in IR2 & IR8, LTC 31/03/2004[O. Brüning] Requirements in ramp & squeeze, LHC MAC 9-11/12/2004[O. Brüning] Squeeze of the crossing scheme in IR1 & IR5, ABP-LOC 11/10/2005[S. Fartoukh] Discussion of the operational procedure for squeezing the beams, ABP-LCU 12/02/2007[S. Redaelli] Progress in IR8 matching for beta* squeeze, ABP-LCU 26/02/2007[Y. Papaphilippou] Final squeeze solution for IP8, ABP-LCU 21/05/2007[Y. Papaphilippou] LHC ramp commissioning, LTC 9/5/2007 [M. Lamont] LHC Orbit Stability during β* Squeeze, LHC Collimation WG 27/11/2006 [R. Steinhagen]