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
LHC Technical Committee, 11/04/2007

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
LHC Technical Committee, 11/04/2007

3. LHC Stage A: Commissioning phases
Phases for full commissioning Stage A (pilot physics run)
Phase
Description
A.1
Injection and first turn:  injection commissioning; threading, commissioning beam instrumentation.
A.2
Circulating pilot: establish circulating beam, closed orbit, tunes, RF capture
A.3
450 GeV initial commissioning:  initial commissioning of beam instrumentation, beam dump
A.4
450 GeV optics: beta beating, dispersion, coupling, non-linear field quality, aperture
A.5
Increasing intensity: prepare the LHC for unsafe beam
A.6
Two beam operation - colliding beams at 450 GeV
A.7
Snap-back and ramp: single beam
A.8
Bringing beams into collision: adjustment and luminosity measurement
A.9
7 TeV optics: beta beating, dispersion, coupling, non-linear field quality, aperture
A.10
Squeeze: commissioning the betatron squeeze in all IP's
A.11
Physics runs: physics with partially squeezed beams, no crossing in IP1 and IP5
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
LHC Technical Committee, 11/04/2007

4. Detailed Measurements at 450 GeV – Overview of Steps Involved
Activity
Priority
A.4.1
Measure & correct closed orbit 1
A.4.2
Measure & correct linear optics (b, D, ...)
A.4.3
Measure and correct transverse aperture
A.4.4
Measure momentum aperture
A.4.5
Commission collimators & protection devices
A.4.6
Detailed rf measurements
A.4.7
Measure & correct global non-linear optics
1 to 3
A.4.8
Commission non-linear correctors
A.4.9
Commission IR bumps 2
A.4.10
Perform injection matching
A.4.11
Beam loss studies
Priority categories (71th LTC):
absolutely mandatory,
should be done if possible,
would be nice if it could be done
LHC Technical Committee, 11/04/2007

5. Detailed Measurements at 450 GeV – 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?)
LHC Technical Committee, 11/04/2007

6. Detailed Measurements at 450 GeV – 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
LHC Technical Committee, 11/04/2007

7. D’d Measurements at 450 GeV – 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
LHC Technical Committee, 11/04/2007

8. D’d Measurements at 450 GeV – 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 = 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
LHC Technical Committee, 11/04/2007

9. D’d Measurements at 450 GeV – 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
LHC Technical Committee, 11/04/2007

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
LHC Technical Committee, 11/04/2007

11. Detailed Measurements at 450 GeV – Stage A.4.1 – Closed Orbit
Step
Activity
Priority
A.4.1
Measure and correct closed orbit 1
A.4.1.1
Measurement and correction of each arc
ABP/OP
A.4.1.2
Measurement & correction of each IR (needs another iteration with 2 beams)
A.4.1.3
Iterate with improved optics knowledge if/as needed 2
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
LHC Technical Committee, 11/04/2007

12. example: A.4.1 – sensitivity of orbit feedback to b beat
R. Tomas,
LHCCWG#8
R. Steinhagen,
LHCCWG#6
LHC Technical Committee, 11/04/2007

13. D’d Measurements at 450 GeV – Stage A.4.2 – Linear Optics
Step
Activity
Priority
A.4.2
Measure and correct linear optics 1
A.4.2.1
Polarity checks of MQT, MQS, MQSX
ABP/OP
A.4.2.2
Coupling
A.4.2.3
Beta beat
A.4.2.4
Dispersion
A.4.2.5
Refined optics model, response matrix, BPM calibration (no beam time)
ABP/BI/OP 2
A.4.2.6
Generation of new settings for correctors if necessary(?)
A.4.2.7
Additional local beta measurements with K-modulation (IR's, wires, collimators, ...)
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
LHC Technical Committee, 11/04/2007

14. example: A.4.2.1 - coupling correction
R. Tomas,
LHCCWG#8
LHC Technical Committee, 11/04/2007

15. example: A.4.2.2 - beta beat correction
R. Tomas,
LHCCWG#8
LHC Technical Committee, 11/04/2007

16. D’d Measurements at 450 GeV – Stage A.4.3 – Transv. Aperture
Step
Activity
Priority
A.4.3
Measure and correct transverse aperture 1
A.4.3.1
Commission sliding bump software
ABP/OP
A.4.3.2
Measure global aperture measurements with kick + loss method and/or by exciting orthogonal correctors
A.4.3.3
Apply local bumps to center orbit in aperture [if needed]
2-1
A.4.3.4
Iteration of A and A until we achieve tolerances [if needed]
A.4.3.5
Commission the aperture database, if available 2
A.4.3.6
Dedicated local aperture measurements (IR's, dump,..)
A.4.3.7
Commission other measurement tools (emit. blow-up, AC dipole), cross checks
ABP/BI/OP 3
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
LHC Technical Committee, 11/04/2007

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
LHC Technical Committee, 11/04/2007

18. D’d Measurements at 450 GeV – A.4.4 – Momentum Aperture
Step
Activity
Priority
A.4.4
Measure momentum aperture 1
A.4.4.1
Radial steering scans (full beam scraping)
ABP/OP
LHC Technical Committee, 11/04/2007

19. D’d Measurements at 450 GeV – A.4.5 – Collimators & PDs
Step
Activity
Priority
A.4.5
Commission collimators & protection devices 1
A.4.5.1
Beam based alignment of required collimators (TCPs, TCDQ, TDIs, TCTs, some TCSs)
Coll. Team
A.4.4.2
Measurements of local beta-functions and beam sizes by collimator scans
A.4.4.3
Enter beam-based information into database, define reference settings, ...
prepare for limited higher stored energies
(ramp or higher intensities at 450 GeV);
may also be done in phase A.5
LHC Technical Committee, 11/04/2007

20. example: A.4.5.1 – beam-based collimator alignment in SPS
S. Redaelli,
Chamonix
2005
LHC Technical Committee, 11/04/2007

21. D’d Measurements at 450 GeV – A.4.6 – RF Measurements
Step
Activity
Priority
A.4.6
Perform detailed RF measurements 1
A.4.6.1
Final commissioning of the radial loop (if not already done) RF
A.4.6.2
Longitudinal profile (parasitic)
LHC Technical Committee, 11/04/2007

22. D’d Measurements at 450 GeV – A.4.7 – Global Nonlinear Optics
Step
Activity
Priority
A.4.7
Measure and correct global nonlinear optics 1
A.4.7.1
Tune versus Dp/p -> Q', Q'', ...
ABP/OP
A.4.7.2
Tune vs amplitude 2
LHC Technical Committee, 11/04/2007

23. D’d Measurements at 450 GeV – A.4.8 – Nonlinear Correctors
Step
Activity
Priority
A.4.8
Commission nonlinear correctors 1
A.4.8.1
Commission control of corrector circuits if not done
ABP/OP
A.4.8.2
Normal sextupole - polarity checks, local measurement and correction
A.4.8.3
Skew sextupole - polarity checks, local measurement and correction 3
A.4.8.4
Normal octupole - polarity checks, local measurement and correction
A.4.8.5
Normal decapole - polarity checks, local measurement and correction
A.4.8.6
Polarity checks of non-linear MQX correctors
LHC Technical Committee, 11/04/2007

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!
LHC Technical Committee, 11/04/2007

25. D’d Measurements at 450 GeV – A.4.9 – IR Bumps
Step
Activity
Priority
A.4.9
Commission IR bumps
1-2
A.4.9.1
Commission separation bumps in all IP's
ABP/OP
A.4.9.2
Commission spectrometer compensation in IR8 2
A.4.9.3
Commission spectrometer compensation in IR2 3
priority depends on spectrometer status & physics plan
LHC Technical Committee, 11/04/2007

26. D’d Measurements at 450 GeV – A.4.10 – Injection Matching
Step
Activity
Priority
A.4.10
Perform injection matching
2-1 A
trajectory, betatron and dispersion; matching with injection (and/or multi-turn) screens; only necessary in case of inacceptable emittance growth
ABP/BT/OP
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
LHC Technical Committee, 11/04/2007

27. D’d Measurements at 450 GeV – A.4.11 – Beam Loss Studies
Step
Activity
Priority
A.4.11
Beam Loss Studies 2 A
Beam loss map studies
Coll. Team/BI A
Estimate collimation cleaning inefficiency
2-3
LHC Technical Committee, 11/04/2007

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.
LHC Technical Committee, 11/04/2007

29. At the end of this phase:
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)
LHC Technical Committee, 11/04/2007

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
LHC Technical Committee, 11/04/2007

31. Pertinent LHCCWG presentations:
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]
LHC Technical Committee, 11/04/2007