LHC Ramp Commissioning

1. LHC Ramp Commissioning Mike Lamont Reyes Alemany-Fernandez Thanks to: Stefano, Verena, Walter

2. LHC ramp commissioning • Ramp generalities • Overall strategy • Beam entry conditions and tolerances • Entry conditions • Procedures • Exit conditions • What’s in place • Upcoming tests LHC ramp commissioning

3. Magnets • The basic design of the LHC ramp (parabolic, exponential, linear, parabolic (PELP)) is designed to: • P: Push up the time in which the snapback is resolved. • E: Constant Bdot – ramp induced coupling current • L: Max dI/dt of MB power converters • P: smooth round off at top energy LHC main dipole proposed baseline current ramping - Bottura, Burla and Wolf LHC ramp commissioning

4. Ramp Construction • Construct idealized MB current function (PELP) using standard prescription (defined in terms of current variation during snapback etc.) • From this generate momentum(t) using averaged calibration curve • Use this a scale parameter for settings generation • Optics defined as a function of time • Design optics • (Note change of IR2 optics) • Circuit currents via FiDeL generated calibration curves LHC ramp commissioning

5. Nominal cycle I ~ t I ~ et I ~ t2 LHC ramp commissioning

6. Possible variations • Skip exponential • Ramp induced inter-strand coupling currents small • Simplifies ramp structure – easier to stop anywhere • Cost – one minute per ramp • Slower snapback • Measurements planned to check dependency • Programmed stop in ramp • Parabolic – (Linear) - Parabolic • Pre-cycle (as entry condition) • Snapback minimization – particularly during commissioning LHC ramp commissioning

7. Stopping with beam in the ramp Used for commissioning of beam dump, beam loss monitors, beam measurements, optics checks, physics... • Must be programmed before starting the ramp • with appropriate round-off behaviour of the functions • Might need to handle (much reduced) decay after the stop • Restart with beam is possible in theory. • requires a new set of functions to be loaded • including corrections for handling the associated snapback • during commissioning will be dumping the beam LHC ramp commissioning

8. Settings/Trim • Run to run feed forward • Feed forward from feedback system • Incorporation of TRIMs into settings before ramping • Ensure and test compatibility with feedbacks and make sure that machine safety cannot be compromised • constant strength, smoothed out etc. as appropriate. • This will be configurable depending on the parameters involved. The appropriate strategy will be decided based on common sense and experience with beam. • Real time knobs on key beam parameters (tune, chromaticity) are planned. To be tested during commissioning. LSA LHC ramp commissioning

9. Magnets • Transfer functions • DC components • Geometric, DC magnetization, Saturation, Residual • MB MQ (Decay &) Snapback predictions • b1, b2, b3, b5, a2, a3… • Cycling prescriptions – all magnets • Corrector Hysteresis • Handled on-line by LSA’s implementation of FiDeL • Snapback “on the fly” invocation and incorporation • Import of FiDEL coefficients into LSA database in progress LHC ramp commissioning

10. Power converters • Load I(t) to all 1700 power converters • Ramp won’t load if I(0) not within 0.01 of actual reference value • 100 µs granularity • up to 5000 points, maximum duration 400000 s. • Linear interpolation of supplied points • FGC runs full table – no stop/re-start • Abort running ramp possible - don’t expect to keep the beam • There can be no trims after loading the ramp • Changes can still be put through the real time channel, however, the real time TRIMs are not ramped • Ramp start on receipt of timing event LHC ramp commissioning

11. RF • Use multiplexed FGCs for function generation • The FGC2_RF will generate sixteen 16-bit integer functions at 1 kHz and will use the RFC-500 card to distribute the function values to the relevant nodes on the bus • Will ramp: • 2*8*Cavity voltages & phase • Coupler positions • RF frequency (offset from 400 MHz). Both rings nominally locked to the same frequency to avoid re-phasing before physics • gain of the phase loop • gain and time constant of the synchro loop • Plus transverse damper etc. LHC ramp commissioning

12. Radial Loop • Fixed radial position, variable frequency • Adjusts RF frequency to centre beam at pickup in IR4 • measure frequency offset and feed correction forward into functions [LSA] • Choices • Single pickup as planned • Global orbit average – correct via RT system (robust) • Two pick-ups at Pi • Feed forward – check mean orbit – implies RT global orbit acquisition – correct either radial loop reference or frequency LHC ramp commissioning

13. Beam Dump • Loaded with the reference energy ramp • On-line secure energy monitoring • MSD/Q4 – FGC – I(t) locked in • MKD, MKB kicker and MSD septum energy tracking • Extract single pilot at pre-defined energies in the ramp (calibrated points) • Check MKD kicker “fine” timing adjustment Orbit/aperture Extraction trajectory Instrumentation Kicker timings, retriggering Post mortem and XPOC Brennan Goddard Cham 2006 LHC ramp commissioning

14. LBDS beam commissioning – pilot beam = time consuming LHC ramp commissioning

15. Collimators • Motor positions(t) down loaded to controllers • Functions triggered with timing event • Settings maintained on LSA with full parameter space defined (position, angle, emittance, Twiss etc.) • High Intensity ramp behaviour defined • C. Bracco: Collimator settings during the energy ramping • Low Intensity ramp commissioning • Cleaning not an issue, protection. • Set TCDQ/TCS at ±10 s at 450 GeV, primary at 7-8 s • Good enough for intermediate energies • Provides protection at 7 TeV, but still might want to bring them in Stefano and Delphine LHC ramp commissioning

16. Timing System • Timing table(s) pre-configured and loaded to the CBCM • Start PC ramp • Start RF ramp • Start collimator ramp • BPM – closed orbit/capture • BLM – burst • Fly Wire Scanner • Etc. etc. • Executed on request by timing system LHC ramp commissioning

17. Measurements on ramp • Periodic • BCT/Lifetime • Synchrotron light monitors • Beam Loss Monitors • Schottky • WCM • Continuous • Tune PLL – clear priority • Chromaticity • RF modulation (Synch with orbit -> dispersion) • Ramp – different frf • “Slow” orbit acquisition ~ 1 Hz • RT orbit acquisition ~10 Hz LHC ramp commissioning

18. Measurements at intermediate energies • Tunes, Chromaticity, Orbit, Coupling • Tracking between sectors • Transfer functions • Beta beating LHC ramp commissioning

19. Tune feedback requirements Stable PLL tune measurement system Knowledge of correction quad transfer functions already known from initial tune corrections Implementation of feedback controller Coupling feedback requirements Stable PLL tune measurement system Knowledge of skew quad transfer functions Implementation of feedback controller Chromaticity feedback requirements Stable PLL tune measurement system RF frequency modulation All of these will require dedicated beam time for testing the control loop response and the final closing of the loop. Feedback using the PLL tune system Rhodri Jones LHC ramp commissioning

20. Machine Protection Start Low intensity, single bunch, low energy... same as at 450 GeV • BLMs: acquisition – no dump, check losses against thresholds • collimators & TDCQ coarse settings Switch to nominal cycle Single beam through snapback Critical machine protection systems must be in place • minimum subset of BLMs connected to beam interlock system • collimators interlocked in place • local orbit stabilisation around beam cleaning insertions and dump region • further commissioning of beam dump & BLMs • BEM & SBF Ramp – single beam Single beam to physics energy Two beams to physics energy End LHC ramp commissioning

21. Overall strategy

22. Initial Ramp Commissioning • Baseline 450 GeV commissioning • Snapback light pre-cycle • Pilot beam • Wait it out at injection • Snapback using FiDeL predictions • Ramp to reduced energy • Recycle full machine • Thus in seven steps with seven ramps to seven TeV • Repeat for beam 2 LHC ramp commissioning

23. Procedures

24. LHC Stage A: Commissioning phases • Commission snap-back corrections • Commission the RF up to top energy • Commission beam dump and machine protection (MPS) at different intermediate energies • Commission BI acquisition in the ramp Snap-back & Ramp with single pilot beam – Basic Objectives LHC ramp commissioning

25. Overview of Steps Involved LHC ramp commissioning

26. Beam Entry Conditions Beam Entry conditions: • One bunch, Ib = 5x109 p to 3x1010 p • Separate commissioning for beam 1 and beam 2 • Nominal beam emittance (value agreed for ramping) Beam tolerances: • 450 GeV tolerances should also apply for the ramp as the available beam aperture stays constant • Need to allocate budgets for static and dynamic tolerances • Relaxed tolerances on key beam parameters LHC ramp commissioning

27. Entry conditions LHC ramp commissioning

28. Entry conditions LHC ramp commissioning

29. Entry conditions LHC ramp commissioning

30. Stage A.8.1 – Prepare ramp LHC ramp commissioning

31. Stage A.8.1 – Prepare ramp LHC ramp commissioning

32. Stage A.8.2 – Ramp single beam LHC ramp commissioning

33. Stage A.8.2 – Ramp single beam LHC ramp commissioning

34. Stage A.8.2 – Ramp single beam LHC ramp commissioning

35. Stage A.8.3 – Post Ramp analysis LHC ramp commissioning

36. Stage A.8.4 – Beam at Intermediate Energy LHC ramp commissioning

37. Stages A.8.5 – A.8.7 • A.8.5 Iterate: • Dump at progressively higher energies: • proposal: 7 steps from 450 GeV to 7 TeV • Repeat previous stages at each benchmark energy • The full procedure will have to be repeated for beam 2 • A.8.6 Commission Collimators in the ramp (Group Coll) • Procedure should have essentially been commissioned without beam • Watch closed orbit at collimators and related beam losses • No cleaning issue for pilot.. Primary needs to be defined • 10 sigma TCDQ at 450 GeV, primary closer – could leave for first attempts • based on findings during 450 GeV optimization • A.8.7 Commission Feedback using PLL (Group BI) • If at first you don’t succeed LHC ramp commissioning

38. Exit Conditions • Reasonable transmission of pilot through snap-back (first minute of the ramp) • Single pilot at 7 TeV – ramp transmission good enough to get pilot intensity up • Beam dumps commissioned up to 7 TeV • Machine Protection good for these intensities to 7 TeV • At the end of this phase: - we can proceed with top energy checks with single beam LHC ramp commissioning

39. What have we got?

40. Settings Generation • Optics & Twiss import • Ramp & squeeze – all circuits • Fully integration of LHC power converters • Ramp and squeeze tests performed. • Driven by proto-sequencer • Collimators • Inc. parameter space – Twiss parameters as functions • RF • Incoming • BLMs • Just started wrestling with the threshold tables LHC ramp commissioning

41. Collimators Stefano Redaelli LHC ramp commissioning

42. Ramping – IR8 LHC ramp commissioning

43. FiDeL Marek LHC ramp commissioning

44. Timing Delphine Jacquet LHC ramp commissioning

45. Sequencer • Requirements specification • Mike, Reyes & Fermilab • First prototype in place • Tasks, sub-sequences, sequences, external conditions defined on database • Demo Vito Baggiolini Roman Gorbonosov Reyes Alemany Greg Kruk Mike Lamont LHC ramp commissioning

46. Upcoming tests • Ramp and squeeze tests during HWC • Ongoing • Ramp tests in SM18 • Hit instrumented MBs, MQ • Effects of different pre-cycles etc. etc. • Stephane Sanfilippo et al. • Dry magnet sector test • Other systems • Hardware tests during HWC LHC ramp commissioning

47. Conclusions • Principles and mechanics understood • Procedures for initial commissioning pretty well established • Implementation of tools in progress • Tests planned LHC ramp commissioning