LHC Commissioning Phases

1. LHC Commissioning Phases Detailed Measurements at 450 GeV presented by Frank Zimmermann on behalf of the LHCCWG Particular thanks to Stefano Redaelli, Massimo Giovannozzi, the EICs, Roger Bailey, Stephane Fartoukh, Brennan Goddard, Rhodri Jones, Verena Kain, Mike Lamont, Ralph Steinhagen, Jan Uythoven, Jorg Wenninger

2. LHC Commissioning Phase 4 – Detailed Measurements at 450 GeV • Phase A.4: Detailed Measurements at 450 GeV • Objectives • Entry conditions • Preconditions and tools • Commissioning procedures with a few examples • Exit conditions • Summary

3. LHC Stage A: Commissioning phases Phases for full commissioning Stage A (pilot physics run) Basic Objectives: • establish linear optics • first assessment of orbit & optics stability • chromaticity control preparing for the ramp • collimator setup in view of higher stored beam energies • aperture validation

4. Detailed Measurements at 450 GeV – Overview of Steps Involved • Priority categories (71th LTC): • absolutely mandatory, • should be done if possible, • would be nice if it could be done

5. Detailed Measurements at 450 GeV – Beam Entry Conditions Beam Entry conditions: • both beams circulating with lifetime > 1h • separate commissioning for beam 1 and beam 2 • some steps require both beams simultaneously (1) orbit/optics correction in the common regions; (2) D1/D2 transfer function checks; (3) Parallel separation bumps. • coasting beams (LHC) and Inject&Dump mode (few s) • only single bunches, intensities up to a few 1e10 protons • nominal beam emittance (value agreed for ramping) • reproducible emittance from injector chain • reduced intensity for studies involving full beam loss i.e. momentum aperture, injection failure scenarios; for these use a few 1e9 protons (scraping in the SPS?)

6. Detailed Measurements at 450 GeV – Optics Entry Conditions Optics Entry conditions: • nominal tunes if possible (otherwise, need to first correct coupling on special commissioning working point) • stable/reproducible optics and orbit • reproducible injected beams shot by shot • chromaticity under control

7. D’d Measurements at 450 GeV – RF & Magnets Entry Conditions RF & Magnets Entry conditions: • RF fully commissioned for pilot++ intensities (see A.3) • radial steering fully commissioned • transverse damper commissioned; possibility to switch it ON/OFF • COD polarity checked and calibrated • full HWC of “higher order” corrector circuits & CCC control - lattice correctors: coupling (a2), chromaticity (b3), Landau octupoles (b4) - spool pieces: sextupole (b3), octupole (b4), decapole (b5) - MQX correctors: orbit, coupling, dodecapoles (b6) • detector magnets OFF • spectrometers at IP2 and IP8 OFF • HWC of steering magnets for IP separation/crossing bumps • both signs of IP bumps available

8. D’d Measurements at 450 GeV – Instrumentation Entry Conditions Instrumentation Entry conditions: • BPM system: - polarity & calibration checked; expected resolution for single bunches of 1 to a few 1e10 p: closed orbit = 10 micron; trajectory = 50-100 micron; - sum signal available [imposes constraints for the operation with two beams!] ; - acquisition synchronized with other devices (kickers, wires, ...) ; - turn-by-turn acquisition available; - >1000-turn acquisition; - simultaneous 1000-turn acquisition for both beams • BCT: - DC BCT's cannot be used at pilot or pilot+ intensities; - measurements must rely on the fast-BCT measurements (10% accuracy with 1e10;1% accuracy with 1e11!); - turn-by-turn acquisition synchronized to kicker/bpm/wires/blm • Beam size measurements: - Wire scanners [priority 1]; - Ionization profile monitors (IPM's) [priority 3]; - Synchrotron radiation monitor [priority 2]; Absolute calibration <~20% for the beam size; What is the minimum time between consecutive measurements? (Implications, e.g. on the minimum rise-time of orbit bumps to measure beam profiles before and after beam scraping) • Beam loss monitors: - Signal acquisition for all the available monitors; - Movable monitors ready for use; - Dedicated fast acquisitions with t_acq<20ms • Screens:Emittance measurements in the TL for pulse-to-pulse monitoring

9. D’d Measurements at 450 GeV – Controls Entry Conditions Controls Entry conditions: • YASP steering program (already available): - Correct and steer the closed orbit; Correct and adjust single (first) turn (e.g., re-tuning of injection areas after orbit bumps); 3- and 4-corrector bumps with variable amplitude; optics model to calculate Dp/p • Automatic application for SLIDING BUMPS; could be part of YASP or use YASP • Collimator control software • Control, acquisition, display and logging of all required BI monitors (BPM, BCT, BLM, wires, etc...) and devices (tune kickers, aperture kickers, ...); Simultaneous data taking is crucial! • "Aperture database" - Online update for "as-measured" aperture model (location of aperture bottlenecks, bump settings that optimize aperture). • (On-line) optics model to get (propagate) optics - MAD-X online model or multi-turn application with MAD-X interface • Control of AC dipole from Q meter; AC dipole interlock commissioned

10. D’d Measurements at 450 GeV – Addt’l HW Entry Conditions Additional Hardware Entry conditions: • tune/aperture kickers (commissioned already in A.3) • first use of collimator subset • beam scraping at the SPS (generate "pencil" beams or small emittances) • additional devices for aperture measurements - commissioning of emittance blow up (?); transverse quadrupole noise? RF noise? • AC dipole

11. Detailed Measurements at 450 GeV – Stage A.4.1 – Closed Orbit reference closed orbit for the following phases; orbit corrected within tolerance (peak+r.m.s.); measurement accuracy to be defined; much of this done in earlier phases already; first detailed estimates of orbit stability and reproducibility

12. example: A.4.1 – sensitivity of orbit feedback to b beat R. Tomas, LHCCWG#8 R. Steinhagen, LHCCWG#6

13. D’d Measurements at 450 GeV – Stage A.4.2 – Linear Optics reference optics for following phases; beta beat measured (and corrected) within tolerance; dispersion measured (and corrected) within tolerance; b and D are corrected together; first detailed estimates of optics stability and reproducibility; coupling, beta-beat & dispersion correction may need second iteration with 2 beams

14. example: A.4.2.1 - coupling correction R. Tomas, LHCCWG#8

15. example: A.4.2.2 - beta beat correction R. Tomas, LHCCWG#8

16. D’d Measurements at 450 GeV – Stage A.4.3 – Transv. Aperture first global aperture measurements; detailed local aperture measurements in critical locations; optimization of local bottlenecks that become critical at 7 TeV; priority 2 becomes 1 if we squeeze after ramp

17. example: A.4.3.6 – local aperture measurements S. Redaelli, LHCCWG#11 Established methods based on BCTs are also available; inject & dump mode possible

18. D’d Measurements at 450 GeV – A.4.4 – Momentum Aperture

19. D’d Measurements at 450 GeV – A.4.5 – Collimators & PDs prepare for limited higher stored energies (ramp or higher intensities at 450 GeV); may also be done in phase A.5

20. example: A.4.5.1 – beam-based collimator alignment in SPS S. Redaelli, Chamonix 2005

21. D’d Measurements at 450 GeV – A.4.6 – RF Measurements

22. D’d Measurements at 450 GeV – A.4.7 – Global Nonlinear Optics

23. D’d Measurements at 450 GeV – A.4.8 – Nonlinear Correctors

24. example: A.4.8.2 – check of normal sextupole circuits local b3 correction: chromatic phase advance F. Zimmermann, Chamonix 2003; LHCCWG#10 simulated Df for 1s kick for dp/p=10-3 and dp/p=0; 3 cases: (1) no spool piece mispowered, (2) sextupole circuit KCS45 missing (BPMs 194 to 257), (3) decapole circuit KCD45 missing we can detect missing b3 circuits, but not missing b5!

25. D’d Measurements at 450 GeV – A.4.9 – IR Bumps priority depends on spectrometer status & physics plan

26. D’d Measurements at 450 GeV – A.4.10 – Injection Matching acquisition system and software for OTR injection matching monitor available only for LHC Phase II (75-ns operation); fine tuning is done in later phase, e.g. A.5

27. D’d Measurements at 450 GeV – A.4.11 – Beam Loss Studies

28. Detailed Measurements at 450 GeV – Exit Conditions Main exit conditions: Reference orbit and linear optics under control (both beams) as precondition for ramp. Nominal injection optics established. Collimators and protection devices set up for higher stored energies (ramp or intensity increase); - much of this could be done also in A.5 Chromaticity measurements & corrections available for ramp. Machine aperture at injection known. First assessment of stability & reproducibility.

29. Summary • Phase A.4 : • prepare for ramp and for higher intensity • Main focus is on: • orbit control • linear optics control • chromaticity control • aperture control • set up of collimators & protection devices (could be in phase A.5) • stability & reproducibility • At the end of this phase: - we can ramp pilot bunches to 7 TeV (phase A.7) - and/or increase the bunch intensity & # bunches (phase A.5)

30. Comments • Detailed measurements at 450 GeV will probably be interleaved with pilot-bunch ramps to higher energy • Sorting out D1/D2 transfer function errors may later on require measurements with triplet alignment optics at 450 GeV

31. References • Web documentation LHC Commissioning procedures, LHC Commissioning pages Documentation and Procedures: Phase A4 [S. Redaelli, EICs+V. Kain] • Pertinent LHCCWG presentations: Circulating Beam and RF Capture LHCCWG#3 [G. Arduini, A. Butterworth] Magnetic Field Fill-to-Fill Reproducibility and Differences Between the Two Apertures LHCCWG#14 [L. Bottura] Beam Instrumentation - BPM, BLM, BCT, Transverse Diagnostics LHCCWG#3 [R. Jones] Commissioning Procedures LHCCWG#5 & #6 [V. Kain] Snapback and Ramp with Single Beam LHCCWG#7 [M. Lamont] 450 GeV Optics: IR Aperture and IR Bumps LHCCWG#13 [Y. Papaphilippou] 450 GeV Optics – Mechanical Aperture and Momentum Aperture LHCCWG#11 [S. Redaelli], Overview of Feedbacks and Implications for Commissioning LHCCWG#6 [R. Steinhagen] 450 GeV Optics – Beta Beating, Coupling, Dispersion LHCCWG#8 [R. Tomas] Response Matrix Measurements and Analysis LHCCWG#9 [J. Wenninger] Tracking error measurement and correction LHCCWG#17 [J. Wenninger] Nonlinear Field Quality Checks LHCCWG#10 [F. Zimmermann] Initial Measurement Program LHCCWG#3 [F. Zimmermann] Summary of Parameter Tolerances LHCCWG#19 [F. Zimmermann] What to Do If We Cannot Get in Tolerance LHCCWG#19 [F. Zimmermann] Proposed Beam Measurement Program in 2007 LHCCWG#19 [F. Zimmermann] • Others: Field Quality Specification for the LHC Main Dipole Magnets, LHC PR 501 [S. Fartoukh, O. Brüning] Measurement of the Betatron Tunes and of the Chromaticity and Amplitude Detunings in the LHC Rings, LHC-B-ES-000X.00.rev0.2 [S. Fartoukh, J.P. Koutchoukl] Proceedings Chamonix XV Proceedings Chamonix Chamonix XII Procedures and accuracy estimates for beta-beat correction in the LHC EPAC’06 [R. Tomas et al]