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

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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

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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

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Detailed Measurements at 450 GeV Overview of
Steps Involved
Step Activity Priority
A.4.1 Measure correct closed orbit 1
A.4.2 Measure correct linear optics (b, D, ...) 1
A.4.3 Measure and correct transverse aperture 1
A.4.4 Measure momentum aperture 1
A.4.5 Commission collimators protection devices 1
A.4.6 Detailed rf measurements 1
A.4.7 Measure correct global non-linear optics 1 to 3
A.4.8 Commission non-linear correctors 1 to 3
A.4.9 Commission IR bumps 2
A.4.10 Perform injection matching 2
A.4.11 Beam loss studies 2

• Priority categories (71th LTC)
• absolutely mandatory,
• should be done if possible,
• would be nice if it could be done

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Detailed Measurements at 450 GeV Beam Entry
Conditions

• Beam Entry conditions
• both beams circulating with lifetime gt 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 InjectDump 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?)

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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

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Dd 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

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Dd 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 - gt1000-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 1e101
  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 lt20 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_acqlt20ms
• Screens Emittance measurements in the TL for
  pulse-to-pulse monitoring

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Dd 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

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Dd Measurements at 450 GeV Addtl 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

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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 1
A.4.1.2 Measurement correction of each IR (needs another iteration with 2 beams) ABP/OP 1
A.4.1.3 Iterate with improved optics knowledge if/as needed ABP/OP 2
reference closed orbit for the following
phases orbit corrected within tolerance
(peakr.m.s.) measurement accuracy to be
defined much of this done in earlier phases
already first detailed estimates of orbit
stability and reproducibility
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example A.4.1 sensitivity of orbit feedback to
b beat
R. Tomas, LHCCWG8
R. Steinhagen, LHCCWG6
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Dd 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 1
A.4.2.2 Coupling ABP/OP 1
A.4.2.3 Beta beat ABP/OP 1
A.4.2.4 Dispersion ABP/OP 1
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(?) ABP/OP 2
A.4.2.7 Additional local beta measurements with K-modulation (IR's, wires, collimators, ...) ABP/OP 2
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, LHCCWG8
15
example A.4.2.2 - beta beat correction
R. Tomas, LHCCWG8
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Dd 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 1
A.4.3.2 Measure global aperture measurements with kick loss method and/or by exciting orthogonal correctors ABP/OP 1
A.4.3.3 Apply local bumps to center orbit in aperture if needed ABP/OP 2-1
A.4.3.4 Iteration of A.4.3.2 and A.4.3.3 until we achieve tolerances if needed ABP/OP 2-1
A.4.3.5 Commission the aperture database, if available ABP/OP 2
A.4.3.6 Dedicated local aperture measurements (IR's, dump,..) ABP/OP 2
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
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example A.4.3.6 local aperture measurements
S. Redaelli, LHCCWG11
Established methods based on BCTs are also
available inject dump mode possible
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Dd 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 1
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Dd 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 1
A.4.4.2 Measurements of local beta-functions and beam sizes by collimator scans Coll. Team 1
A.4.4.3 Enter beam-based information into database, define reference settings, ... Coll. Team 1
prepare for limited higher stored energies
(ramp or higher intensities at 450 GeV) may
also be done in phase A.5
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example A.4.5.1 beam-based collimator
alignment in SPS
S. Redaelli, Chamonix 2005
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Dd 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 1
A.4.6.2 Longitudinal profile (parasitic) RF 1
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Dd 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 -gt Q', Q'', ... ABP/OP 1
A.4.7.2 Tune vs amplitude ABP/OP 2
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Dd 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 1
A.4.8.2 Normal sextupole - polarity checks, local measurement and correction ABP/OP 1
A.4.8.3 Skew sextupole - polarity checks, local measurement and correction ABP/OP 3
A.4.8.4 Normal octupole - polarity checks, local measurement and correction ABP/OP 3
A.4.8.5 Normal decapole - polarity checks, local measurement and correction ABP/OP 3
A.4.8.6 Polarity checks of non-linear MQX correctors ABP/OP 3
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example A.4.8.2 check of normal sextupole
circuits
local b3 correction chromatic phase advance
F. Zimmermann, Chamonix 2003 LHCCWG10
simulated Df for 1s kick for dp/p10-3 and
dp/p0 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!
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Dd 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 1-2
A.4.9.2 Commission spectrometer compensation in IR8 ABP/OP 2
A.4.9.3 Commission spectrometer compensation in IR2 ABP/OP 3
priority depends on spectrometer status physics
plan
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Dd Measurements at 450 GeV A.4.10 Injection
Matching
Step Activity Priority
A.4.10 Perform injection matching 2-1
A.4.10.1 trajectory, betatron and dispersion matching with injection (and/or multi-turn) screens only necessary in case of inacceptable emittance growth ABP/BT/OP 2-1
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
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Dd Measurements at 450 GeV A.4.11 Beam Loss
Studies
Step Activity Priority
A.4.11 Beam Loss Studies 2
A.4.11.1 Beam loss map studies Coll. Team/BI 2
A.4.11.2 Estimate collimation cleaning inefficiency Coll. Team/BI 2-3
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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.

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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)

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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

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References

• Web documentation
• LHC Commissioning procedures,
• LHC Commissioning pages
• Documentation and Procedures Phase A4 S.
  Redaelli, EICsV. Kain
• Pertinent LHCCWG presentations
• Circulating Beam and RF Capture LHCCWG3 G.
  Arduini, A. Butterworth
• Magnetic Field Fill-to-Fill Reproducibility and
  Differences Between the Two Apertures
• LHCCWG14 L. Bottura
• Beam Instrumentation - BPM, BLM, BCT, Transverse
  Diagnostics
• LHCCWG3 R. Jones
• Commissioning Procedures LHCCWG5 6 V.
  Kain
• Snapback and Ramp with Single Beam LHCCWG7 M.
  Lamont
• 450 GeV Optics IR Aperture and IR Bumps
  LHCCWG13 Y. Papaphilippou
• 450 GeV Optics Mechanical Aperture and Momentum
  Aperture LHCCWG11 S. Redaelli,
• Overview of Feedbacks and Implications for
  Commissioning LHCCWG6 R. Steinhagen
• 450 GeV Optics Beta Beating, Coupling,
  Dispersion LHCCWG8 R. Tomas
• Response Matrix Measurements and Analysis
  LHCCWG9 J. Wenninger
• Tracking error measurement and correction
  LHCCWG17 J. Wenninger
• Nonlinear Field Quality Checks LHCCWG10 F.
  Zimmermann