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Extended LTC: Proposed Tests With Beam Massimo Giovannozzi

Detailed analysis and boundary conditions for sector tests at the LHC, including injection, optics measurements, magnetic cycle, and aperture checks. Key systems, conditions, and strategies covered for successful testing.

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Extended LTC: Proposed Tests With Beam Massimo Giovannozzi

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  1. Proposed tests with beam Massimo Giovannozzi Acknowledgements: G. Arduini, B. Goddard, M. Lamont, S. Redaelli, N. Sammut, J. Uythoven, J. Wenninger. M. Giovannozzi - Extended LTC

  2. Evolution of sector test proposals • 2006: • Detailed analysis presented at the Chamonix Workshop. • 2007: • Sector test without triplets and D1 in IP8 (right). Option quickly discarded. • LHC MAC presentation (M. Lamont). • 2008: • Extensive analysis of various phases of LHC commissioning performed by LHCCWG: sector test would allow applying procedures that will be needed later. • Beam 1 is also considered in the general scheme of a sector test. M. Giovannozzi - Extended LTC

  3. Brief summary of the items/systems to consider • Injection and threading • Instrumentation • Optics measurements • Aperture checks • Effect of magnetic cycle • Field quality checks • Quench limits and BLM response • Others M. Giovannozzi - Extended LTC

  4. Boundary conditions - I See presentation by H. Vincke • LSS and arc(s) should not be irradiated • LHCb should also be preserved • This can be achieved by: • Minimising losses • Optimising/minimising the amount of beam used for the tests. • The beam parameters are • Pilot beam is the preferred choice: 5 x 109 p+, below quench limit, about x100 below damage threshold • Some tests with 1-3 x 1010 or up to 1 x 1011 p+ in one bunch • Beam emittance: 1 mm < en < 3.5 mm (lower emittances might be problematic for machine protection…) • Momentum spread: nominal, but smaller might be useful… M. Giovannozzi - Extended LTC

  5. Boundary conditions - II • Optics • Nominal one: (nx, ny) = (0.28, 0.31). • Commissioning one: (nx, ny) = (0.285, 0.385). To be used only in case of problems. • Other conditions • Start with zero separation/crossing angle to maximise aperture • LHCb spectrometer will be off • Beam losses across LHCb should be quantified (BPM intensity signals are an option) • Circuits used: those already foreseen in Phases A.1 and A.2 (one single beam, only). • Circuits should be commissioned at least to 450 GeV+ for limited recycling. M. Giovannozzi - Extended LTC

  6. LHC magnetic cycle • Start beam tests using the ‘nominal’ cycle: • MB current cycled to < 100% (reduced HWC?) • Cycle correctors to 100%, to avoid over-large hysteresis effects • A ‘de-Gauss’ cycle might be used in a second stage to check the geometric field quality of the magnets. Sector 7-8 Nominal - waiting de-Gauss Recent studies revised the expected decay to smaller values (N. Sammut et al. EDMS 842273): see following slides. Nominal M. Giovannozzi - Extended LTC

  7. End of TL/injection commissioning Right of IP8 (H plane) D2 Q5 Q4 TDI (MKI +90˚) MSI MKI Left of IP2 (H plane) M. Giovannozzi - Extended LTC

  8. Arc(s) Courtesy M. Lamont X 23 M. Giovannozzi - Extended LTC

  9. TL re-commissioning, end of TL and injection commissioning • 24 hours foreseen (Of course, it might be much faster if everything works according to specs…) • Key hardware systems • TL elements (including TCDI), MSI, MKI, Q5+Q4+D2 on injection side (Right for IP8, Left for IP2), correctors, TDI, BTV, BPM, BLM, timing • Dedicated or expert application software • Injection steering, injection post-mortem, TDI positioning, injection fixed displays, equipment expert applications • Crucial issues • Tight aperture at MSI, Q5, MKI, and D2 • Synchronised shot-by-shot logging for each injection M. Giovannozzi - Extended LTC

  10. Aperture bottlenecks Aperture situation in IP2 (similar in IP8). See J. Uythoven, InjWG 13/09/2007 Proposal to change longitudinal angle of Q5 (IP2 and IP8). See J.-B. Jeanneret, InjWG 29/06/2007 M. Giovannozzi - Extended LTC

  11. Threading to arc(s) - I • Proposed strategy • Inject pilot and measure • Correct over small range (manual BPM rejection) • Iterate • Pay attention to the separation/recombination dipoles (transfer functions…) • Method checked by coupling MADX to YASP steering program, with aperture filter, noise etc. (LHC Beam 1) BPMs : ± 3 mm errors, flat distribution Dipoles : b3 = -20 units (systematic), other components : error table Multipole correctors : OFF Courtesy J. Wenninger M. Giovannozzi - Extended LTC

  12. Threading to arc(s) - II • 24 hours foreseen (see comment on slide 8…) • Key hardware systems • LHC machine… • BPMs, correctors, LHCb radiation monitoring, BLMs, BTVs (in case LBDS is used, also those in LSS7 – right – and in the dump line will be available) • Dedicated/expert application software • YASP, MADX on-line model, BPM intensity acquisition (see next slide...) and signal display. • Models • TL + LHC ring (sequence and aperture model) available • Where to stop: • Beam 1: IR3 • Beam 2: up to TDE M. Giovannozzi - Extended LTC

  13. Threading to arc(s) - III • Monitoring beam intensity during the sector test phases will be crucial for many reasons, e.g.: • Controlling beam losses and correlate them with activation • Aperture measurements (see next slides) • Quench behaviour tests (see Ralph’s presentation) • How to get the intensity information: • BPM in intensity mode: this prevents the signal from the other beam (not a problem for the sector test...). Is this mode operational? • Temporary BCTs (not necessary if dump line is used)? • The selected beam intensity should be high enough to allow for losses (in early stages of the tests) without losing BPM triggering. M. Giovannozzi - Extended LTC

  14. Linear optics tests - I • Trajectory response using correctors and BPMs • BPM + corrector polarity and calibration errors • Phase, coupling, Twiss • Dispersion measurement with dp and BPMs • Betatron matching measurement with BTVs Courtesy B. Goddard M. Giovannozzi - Extended LTC TED TI 8 LHC TED IR7

  15. Linear optics tests - II • 12 hours foreseen • 1-2 x 1010 p+ for improved BPM and BTV response • Semi-automated tests. Efficient tool for quick off-line data analysis • Key hardware systems • BPMs, correctors, BTVs • Dedicated/expert application software • On-line re-matching and analysis tools might not be needed • In general tools were developed (TI8/2 tests in 2004/7) and are under development (e.g., MADX on-line model). M. Giovannozzi - Extended LTC

  16. BLM system tests - I • Get the system up and running, recording losses • Prior calibration with source: expect reasonable numbers quickly • Acquisition and display of beam losses for some monitors • Some crosstalk studies possible (in principle ‘other beam’ monitors available…) Courtesy B.Dehning BLMs will be important for the quench tests! M. Giovannozzi - Extended LTC

  17. BLM system tests - II • Parasitic measurment • Will be plenty of other opportunity for parasitic commissioning • Probably to be organised together with the aperture measurements • Key hardware systems • BLM system • Dedicated/expert application software • BLM displays, MCS, BLM expert applications • Remaining issues/areas for study • Finalise data exchange with control system (logging, Post Mortem, thresholds) • BLM display (prototype for final LHC version?) • Triggering for single-shot logging? • Post Mortem to be tested? M. Giovannozzi - Extended LTC

  18. Aperture measurement • Verify physical aperture as expected (bottlenecks, arc, IP) • First iteration : oscillation from 2 correctors at 90º to probe ‘all’ phases • Second iteration if needed/time available: p bumps (local anomalies, specific regions) Horizontal plane 8 s oscillation Vertical plane 8 s bump Courtesy B. Goddard Expected aperture Need corrector strengths of about 50 mrad M. Giovannozzi - Extended LTC

  19. Momentum measurement • Transmission vs momentum offset by changing SPS RF frequency • Probably limited by TL arc (present measured acceptance ±0.003), hence not too relevant. Courtesy B. Goddard dp/p = 0.004 (1mm en) M. Giovannozzi - Extended LTC

  20. Aperture measurements • 24 hours foreseen • Keep clear of LHCb • 1 mm en for best resolution • Key hardware systems • Correctors, BPMs (some with intensity information), BCTs, BLMs. • Dedicated/expert application software • Need (semi-)automatic applications: • Free oscillations (~5 amplitudes, ~12 phases, 2 planes, ~2 starting locations) • For sliding bumps (~45 correctors, 2 planes, ~5 amplitudes) • NB: the real need of detailed aperture measurements should be evaluated taking into account the general constraint of not irradiating too much the arc(s). M. Giovannozzi - Extended LTC

  21. Quench limits and BLM response • Magnet exposure to beam and BLM response • Golden opportunity to steer beam into magnets…. • 36 hours foreseen • Intensity 11011 p+ (5% of damage level at nominal en) • Higher intensity would require multi-bunch injection to be commissioned (probably not worth it). • See R. Assmann talk for full details M. Giovannozzi - Extended LTC

  22. Effects of magnetic cycle - I • Decay effects: • It depends on IFT/IINJ • It depends on ramp rate. • The decay of b3, usually estimated to 2 units, is indeed only 0.9 units for 10 A/s ramp rate (nominal). • Finally, the actual decay will be very small for IFT < INOM M. Giovannozzi - Extended LTC Courtesy N. Sammut

  23. Effects of magnetic cycle - II • 24 hours foreseen • Variations during decay • Reproducibility • Energy variation on flat bottom • In case, go to a ‘de-Gauss’ cycle • Repeat subset of injection, trajectory and linear optics checks R. Wolf – FQWG meeting September 11th 2007 M. Giovannozzi - Extended LTC

  24. Detailed field errors study– high statistics Kick-response and trajectory analysis • LOCO - average a2, b2 and b3 field errors of MBs, b2 of MQs • Need BPM noise & injection errors <200 mm (or ~0.2 s) • Extending method to check multipole corrector polarities (by strong excitation) might be envisaged • 12 hours foreseen • Should plan part of this fairly early, to test method In sector 7-8, actual b3 will be 2-3 times smaller: a stronger kick will be needed! MB b3 field error effect (mean -9.6 units, rms 1.4 units). H trajectory change for 40 mrad H kick (top) and 40 mrad V kick (bottom) M. Giovannozzi - Extended LTC Courtesy J. Wenninger

  25. Other studies • Transfer line collimation studies • Injection protection studies • Impact of MKI wave form on injection performance • Separation and crossing angle bumps (these are not needed for Phase A) • Injecting onto vertical separation bump • Bump closure, induced dispersion, aperture M. Giovannozzi - Extended LTC

  26. Example: separation and crossing bumps • 6 hours • LHCb spectrometer + compensation off • Injecting onto separation bump • Bump closure, induced dispersion, aperture • Injecting onto opposite polarity bump Vertical aperture with 100% bump H&V bumps M. Giovannozzi - Extended LTC

  27. Beam tests summary - I Courtesy M. Lamont M. Giovannozzi - Extended LTC

  28. Beam tests summary - II Courtesy M. Lamont M. Giovannozzi - Extended LTC

  29. Procedure for a sector test? • Since 2006 the LHC Commissioning Working Group studied and prepared detailed procedures for the various phases of the LHC commissioning. • The sector test will allow gaining experience with the procedures for the later stages. Phases for full commissioning Stage A (pilot physics run) M. Giovannozzi - Extended LTC

  30. Entry conditions for commissioning end of TL, injection, threading - I Some collimators will be fully closed to stop the beam (see talk by S. Redaelli) M. Giovannozzi - Extended LTC

  31. Entry conditions for commissioning end of TL, injection, threading - II Partial hardware commissioning and unavailability of some sectors (LBDS not usable) will relax some constraints with respect to Phase A.1 M. Giovannozzi - Extended LTC

  32. Entry conditions for commissioning end of TL, injection, threading - III LBDS might not be needed unless sector 6-7 (Beam 2 tests) will be available (and also in this case there might be alternatives… M. Giovannozzi - Extended LTC

  33. Breakdown of activities - I M. Giovannozzi - Extended LTC

  34. Breakdown of activities - II In case the LBDS could be used… M. Giovannozzi - Extended LTC

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