Title: LHC Commissioning Phases
1LHC Commissioning Phases
- Circulating pilot and RF capture
- presented by G. Arduini
- for the LHCCWG members
- Many thanks to the EICs V. Kain, R. Bailey, P.
Baudrenghien, L. Bottura, O. Brüning, A.
Butterworth, S. Fartoukh, R. Jones, E.
Shaposhnikova, J. Uythoven, J. Wenninger, F.
Zimmermann.
2LHC Commissioning Phases Phase 2 Circulating
pilot and RF capture
- Phase A.2 Circulating pilot and RF capture
- Entry and exit conditions
- Objectives
- Preconditions and tools
- Equipment state/readiness (exit from machine
checkout) - Controls, software and tools
- Machine setup
- Beams, cycles and modes
- Basic settings
- Commissioning procedure
- Breakdown
- Details of some steps
- Possible problems
- Outstanding issues
- Summary
3LHC 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
Phases for proposed 2007 engineering run
Phase Beam time days Beam
A.1 Injection and first turn 4 1 x pilot
A.2 Circulating beam 3 1 x pilot
A.3 450 GeV initial 3 1 x pilot
A.4 450 GeV optics 4 1 x pilot
A.6a 2 beam operation 1 2 x pilot
A.6b Collisions 1 2 x pilot ?
16
4Circulating pilot and RF capture exit and entry
conditions
- Entry conditions
- First turn completed
- RF OFF
- Exit conditions
- Beam circulating for few hundred turns and RF
captured - Ready for set-up of the instrumentation for
circulating beam and more detailed optics
measurements (following 2 phases)
5Circulating pilot and RF capture basic
objectives
- Establish closed orbit
- Commissioning of additional instrumentation
- BPM intensity acquisition
- Preliminary orbit, tune, coupling and
chromaticity adjustments - Obtain circulating beam (few hundred turns at
least) - SPS-LHC energy matching
- Commissioning of RF capture
6Circulating pilot and RF capture basic
objectives
- Tolerances we aim at for this phase
- Closed orbit corrected down to 1-2 mm r.m.s.
- Maximum acceptable radial offset 0.5 mm
- Tune 64.28/59.38 (tune for commissioning) within
few 0.01 - Octant-to-octant MB field offset to few 10-4
- Chromaticity to 10-20 units (to minimize
decoherence of oscillations 1000 turn dynamic
aperture requires Qlt80) - Coupling to few 0.01
- SPS-LHC energy matching to few 10-4
O. Bruning, Chamonix 2003 S. Fartoukh, M. Hayes,
LCC31
7Circulating pilot and RF capture Objectives
Assume that priority 1 objectives of phase A.1
have been achieved
Objective Priority
O.A.2.1 Machine parameters according to tolerances 1
O.A.2.2 Beam captured 1
O.A.2.3 Beam instrumentation
.01 BPM acquisition, intensity mode 1
.02 DC-BCT acquisition, first calibration 2
O.A.2.4 Measurements
.01 Polarity/cabling errors check for correctors and BPMs 1
.02 MQs checked for major errors (integer tune and optics) 1
.03 MBs Energy mismatch between arcs and SPS to LHC corrected to few 10-4 1
.04 Fast physical aperture scans, free oscillations with BPM intensity meas. 1
.05 Systematic physical aperture scans with sliding p bumps 2
.06 Systematic linear optics measurements 2
O.A.2.5 Machine protection
.01 Beam dump synchronization 1
8Circulating pilot and RF capture Objectives
Objective Priority
O.A.2.6 Controls and applications
.01 RF signals and triggers in OASIS (phase pick-up, wall current monitor, peak detected signal, frev, fRF,.) available 1
.02 Synchronization diagnostics tools available 1
.03 RF controls (frequency, voltage, phase, bucket position, ..) 1
.04 Multi-turn trajectory acquisition 1
O.A.2.7 RF systems
.01 RF cavities operational with pilot bunches 1
.02 Phase-loop operational 1
.03 Observation equipment set-up (wall-current monitor) 1
.04 Bucket counting and bunch reference numbers set-up 1
.05 Fine synchronization SPS/LHC commissioned 1
O.A.2.8 Magnets
.01 List of CODs that are found wrong (polarity and coarse calibration) - systematic 1
.02 MQs Major errors disturbing integer tune found and possibly corrected 1
.03 MBs Energy mismatch (inter-arcs, SPS to LHC) corrected to few 10-4 1
.04 MBs Stability of injection after recycling magnets 2
9Circulating pilot and RF capture Equipment
state and readiness (entry)
Assume that entry conditions for phase A.1 have
been met
Entry condition
E.A.2.1 Full LHC checkout and operations dry run (same as E.A.1.1)
E.A.2.2 Application SW
.01 Multi-turn trajectory acquisition
E.A.2.3 Timing system
.01 Interleaved injection
E.A.2.4 Machine protection subsystems (same as E.A.1.4)
E.A.2.5 Collimators (same as E.A.1.5)
E.A.2.6 Magnets (same as E.A.1.6)
E.A.2.7 Injectors and transfer lines
.01 B-field trim tested with beam in SPS/TI2/TI8.
E.A.2.8 Injection equipment (same as E.A.1.8)
E.A.2.9 Beam Instrumentation
.01 Mobile BLMs calibration, acquisition, application
E.A.2.10 Experiments (same as E.A.1.10)
E.A.2.11 RF system
.01 RF cavities conditioned and operating to max. voltage without beam.
.02 RF synchro-loop commissioned
E.A.2.12 Beam Dump system (same as E.A.1.12)
E.A.2.13 Technical services available (same as E.A.1.13)
10Circulating pilot and RF capture Controls,
software and tools
- Some additional key elements for the Circulating
beam and RF capture phase - Fast Analog Signals available in CCC (OASIS) and
Pt. 4 (scopes) - Tools to measure the beam phase shift per turn
w.r.t. the reference RF frequency signal - Multi-turn trajectory acquisition
- YASP for closed orbit measurement and correction
(including closure) - LSA applications, in particular
- Knob for B-field correction (affecting all
magnetic elements) by octant and for the overall
machine. - Knob for Bdl trim with orbit correctors for the
two beams - LOCO available for orbit response analysis
- Online MADX model available
- Online aperture model available
11Circulating pilot and RF capture Beams, cycles,
modes,
- Beam type pilot
- Ib 5 ?109 p
- en 0.3 3.5 mm.mrad (small en in case of
problems) - eL 0.25 0.8 (we can probably go to 2.5) eV.s
- Dp/p 0.15 0.6 ?10-3 (r.m.s.)
- LHC mode inject and dump (set 10-1000 turns)
- a) One ring, single injection on demand
- b) One ring, repeated injection
- c) Two rings, interleaved repeated injection
- Available operational cycles, modes and states
(as for injection commissioning) - Cycle Nominal cycle and wait (gt 20 mins after
injection level achieved) - Occasional re-cycle (in particular during the
energy matching) - Machine protection as for injection commissioning
- Beam dump and LHC mode Inject and Dump allows
screens to be in. Here screens should be OUT and
we should have an alarm or interlock when they
are IN.
12Circulating pilot and RF capture Machine set-up
- Machine set-up as for first turn commissioning,
in particular - Sextupole spool pieces ON and at nominal settings
(from magnetic measurements) - Lattice sextupoles ON and at nominal setting (to
correct for natural chromaticity) - Skew quads ON and at nominal settings (from
magnetic measurements) - Expected machine settings with this configuration
H V
Coupling lt0.1 lt0.1
Chromaticity (spool pieces and lattice sextupoles) assuming 20 error in the b3 estimate 0 /- 20 0 -/ 20
Chromaticity (no correction) -180 0
13Circulating pilot and RF capture Breakdown
Step Activity Priority
A.2.1 Instrumentation and corrector checks (unless completed in phase A.1) (Interleaved)
.01 Commission interleaved injection ST/CO 1
.02 Commission BPM intensity measurement mode BI 1
.03 Systematic BPM/corrector polarity/plane/ring checks and repairs ST 1
.04 Systematic BPM/corrector preliminary calibrations (by-product offline) ABP/OP 2
A.2.2 Establish closed orbit (one beam at a time)
.01 Close the trajectory ST 1
.02 Closed orbit measurement and correction to get few turns ST 1
.03 Fast physical aperture scans, free oscillations with BPM intensity meas. ST 1
.04 Systematic physical aperture scans with sliding p bumps ST 2
A.2.3 Measurements with few turns (one beam at a time)
.01 Integer tune measurement and correction from difference orbit ST 1
.02 Fractional tune measurement from injection oscillation ST 1
.03 Adjustment of chromaticity to reduce de-coherence ST 1
.04 Adjustment of the coupling to reduce CTA ST 1
.05 Systematic linear optics checks ABP/OP 2
STShift Team
14Circulating pilot and RF capture Breakdown
Step Activity Priority
A.2.4 Offsets between different sectors (interleaved)
.01 Correction of the orbit to 1-2 mm r.m.s. ST 1
.02 Correction of the Bdl sector-by-sector down to few 10-4 ST 1
.03 Correction MQ-MQ offsets sector-by-sector from phase advance measurement ST 2
A.2.5 RF commissioning with beam (one beam at a time)
.01 Set-up observation equipment and bunch reference numbers RF 1
.02 Synchronize beam dump kickers RF/BT 1
A.2.6 SPS-LHC Energy matching (mostly interleaved)
.01 Centre first turn in both rings ST 1
.02 Measure revolution frequency for both beams ST/RF 1
.03 Correct (BdlSPS, BdlLHC1,BdlLHC2, fRF_SPSLHC) ST/RF 1
.04 RF ON and Adjust RF phases ST/RF 1
.05 Set-up phase loop (gain, offsets, etc) RF 1
.06 Measure residual energy error and correct ST/RF 1
A.2.7 Measurement with captured beam (interleaved)
.01 Check orbit (average from multi-turn) after capture ST/RF 1
.02 Correct tune-split ST/RF 1
15Circulating pilot and RF capture details
- Instrumentation and corrector checks (unless
completed in phase A.1) - BPM intensity measurement is surely important at
this stage (if not earlier) to determine
potential bottle-necks (in particular soft ones)
and to select the data to be retained for the
turn-by-turn trajectory data averaging - Systematic BPM sanity check (polarity, control
chain, plane, ring and other cabling errors) 2
shifts (R. Steinhagen, F. Zimmermann) is
necessary for the following steps. - This could also provide BPM and corrector
calibration and data for off-line linear optics
check that could then be made available early in
the commissioning in case of problems.
16Circulating pilot and RF capture details
- Establish closed orbit
- Measure integer tune from first turn difference
for two different injection settings and correct
if necessary - Close the trajectory on itself with 2 correctors
from difference of 2 consecutive turns (at least
a few BPMs after the injection point must provide
data in the second turn) ? YASP - Closed orbit measurement (average of turn-by-turn
data over the number of turns available). The BPM
system can cope with an increase in r.m.s. bunch
length st from 0.4 to 1.3 ns. ? - 140 turns for nominal momentum spread. About 280
turns by reducing the momentum spread at
extraction from the SPS by using pilot with 0.25
eV.s and reducing the RF voltage to 2MV at SPS
extraction. - We should then aim to correct the orbit with a
small number of correctors to avoid biasing the
momentum offset determination among sectors later
(A.2.4)
17Circulating pilot and RF capture details
- Measurements with few turns
- If it has not been determined from first turn
data the integer tune can be measured from the
difference of two orbits (one of them with a
distortion from a kick) and harmonic analysis. - Fractional part can be measured by exciting
injection oscillations and comparing turn-by-turn
trajectories or turn-by-turn phase advance
measurements obtained combining the turn-by-turn
data from pairs of BPM separated by 900 in phase
advance. The precision of this measurement is
expected to be DQ0.01 - Adjust the coupling empirically by minimizing the
CTA - Any oscillation will die-out rapidly because of
the de-coherence due to chromaticity - e-folding time 4 turns for QH-179 for
sdE/E03.0610-4 - 43 turns for QH-17, QV17. Can be further
increased by reducing the momentum spread at
extraction from SPS (88 turns for
sdE/E01.510-4). - Adjust the chromaticity empirically by maximizing
the decoherence time - If the lifetime would not be sufficient
systematic linear optics checks might be required
18Circulating pilot and RF capture details
- Offsets between the different sectors
- Once the beam can circulate for a few hundreds
turns the orbit can be measured and corrected
possibly down to 1 mm r.m.s. - In these conditions it should be possible to
correct the relative octant-to-octant MB field
offset to few 10-4 - The B-field trim should be propagated to the
multipoles (at least quadrupoles) to keep the
correct MQ-MB tracking - MQ-MQ tracking might be difficult to correct at
this stage unless the coupling has been minimized
J.Wenninger LHCCWG 17
19Circulating pilot and RF capture details
- SPS-LHC energy matching
- Before the energy matching can start the beam
must survive for at least ¼ of a synch. period
(45 turns at nominal voltage 8MV, about 35
turns at 16 MV). - Starting point beam centred in the SPS at
extraction and in the LHC for both rings (RF
OFF). Pilot beam with small momentum spread. - Assumed common frequency for B1 and B2 in SPS-LHC
(fSPSLHC). Assume same magnetic field at
extraction from the SPS for B1 and B2 - Measure frevLHCi (i1,2) by observing bunch slip
w.r.t. SPS-LHC reference frequency fSPSLHC/hLHC
(either looking at bunch on longitudinal pickup
or at phase detector) vs. time
- Trim fSPSLHC, the LHC integrated field for B1
and B2 (via the CO correctors only), and the
magnetic field at extraction in the SPS ? - There will be a radial offset at extraction in
the SPS if CLHC¹27/7 CSPS (this seems to be the
case) - There will be a radial offset in the LHC after
capture only if the two rings have a different
circumference (0.1 mm for 1.5 mm difference)
20Circulating pilot and RF capture details
- SPS-LHC energy matching (continued)
- Switch the RF ON. It might be worth starting at
maximum voltage (16 MV). - Adjust the RF phases (by using the phase pick-up
signal) - Set-up the phase loop (gain, offsets, etc.)
- Check residual momentum mismatch by observing the
phase pick-up signal (sinusoidal oscillation with
amplitude proportional to the momentum mismatch) - Iterate
- Reduce the voltage to 8 MV (nominal injection
value) or lower
21Circulating pilot and RF capture Possible
problems
- Very low lifetime (few tens of turns)
- Causes Thin obstacle (a phantom valve or other
objects with thickness in the mm range, pressure
bumps), poor optics control - Diagnostic tools check performance with probe
pilot beam (with small transverse and
longitudinal emittances) BLMs, mobile BLMs and
display, BPM intensity mode, radiation survey
piquet, systematic optics measurements from orbit
response analysis. - Remedies obstacle removal, optics correction,
leak fixes - Issues activation of components at problem
location cool-down times - Large coupling
- Causes magnet model uncertainty, wrong MQS
settings, polarity/cabling errors, calibration
errors. - Diagnostic tools cross-plane orbit response with
local bumps at the MQS - Remedies Correction from measurements
- Issues analysis tools
- Large chromaticity
- Causes magnet model uncertainty, wrong MCS/MS
settings, polarity/cabling errors, calibration
errors. - Diagnostic tools phase advance along the ring
vs. momentum offset - Remedies Correction from measurements
- Issues analysis tools
22Circulating pilot and RF capture Possible
problems
- Large path-length difference (gt5 mm) between beam
1 and beam 2 leading to large offsets after
capture - Causes Differences in Bdl among apertures larger
than expected - Diagnostic tools measure the revolution
frequency of the 2 beams with RF off - Remedies Need to have different SPS extraction
magnetic fields for B1 and B2 (2 different
cycles) for the same RF frequency
23Circulating pilot and RF capture Issues
- Software for BPMs in intensity mode
- This is a very useful tool in the SPS at start-up
even after 30 years of operation. - Needed to identify soft bottlenecks and lifetime
problems - Some time is required for the commissioning, but
well spent - Recycling
- How often is recycling required (e.g. if energy
mismatch detected and MBs adjusted)? - Cycling strategy to be fully defined for each
circuit. - We are trying to have a strategy for the
commissioning with beam. Do we have it for the
cold check-out? - From the What if exercise we can learn
something for the cold check-out strategy ? at
least to avoid trivial problems (calibration
curves, wrong settings, ). - Need to create a list of possible errors and
corresponding methods to trace them
24Summary
- Phase A.2 from first turn to basic machine
set-up to obtain circulating beam (few hundred
turns) for RF capture and to open the way to the
next phase focussed on Beam Instrumentation
set-up - Also in this phase aim for simplicity (where
possible) - For some of the steps interleaved injection might
be required - Stay with single pilot bunch
- Systematic measurement limited to the sanity
check of the correctors/BPM required to iron-out
the orbit and to adjust the LHC Bdl - Need to commission the BPM intensity measurement
to identify localized losses that might lead to
low lifetime - Some what-if scenarios elaborated
- We need to create a list of possible errors
(cabling, polarity, etc.) with their effect and
possible means to detect them
25References
- Web documentation
- LHC Commissioning procedures,
- LHC Commissioning pages
- Documentation and Procedures Phase A2
EICsV. Kain - LHCCWG minutes and relevant presentations
- Circulating Beam and RF Capture G. Arduini,
A. Butterworth - Circumference Difference Between the 2 LHC Rings
G. Arduini - Beam Instrumentation - BPM, BLM, BCT, Transverse
Diagnostics R. Jones - Commissioning Procedures V. Kain
- Response Matrix Measurements and Analysis J.
Wenninger - Tracking error measurement and correction J.
Wenninger - Summary of Parameter Tolerances F.
Zimmermann - What to Do If We Cannot Get in Tolerance F.
Zimmermann - Others
- The minimum machine and the first 1000 turns or
so O. Brüning - Commissioning tunes to bootstrap the LHC, LCC31
(23/10/02) S. Fartoukh, M. Hayes - First Turn, LHC Project Note 308 A. Verdier
26- Americas Marine Corps never makes detailed
studies in advance. Leaving important things to
the last minute reduces the risk of wasting time
on things that may ultimately prove not important
at all.
The Economist, Jan 4th, 2007
F. Zimmermann LHCCWG19