DESY Accelerator Physics SeminarFebruary, 9th 2010 1
Operational Experience with the LHC and SPS Tune Resonance Phenomena
Tobias Baer
DESY Accelerator Physics Seminar
February, 9th 2010
DESY Accelerator Physics SeminarFebruary, 9th 2010 2
Content
1. CERN Accelerator Complex
2. Operational Experience with the LHC
3. Tune Resonance Phenomena in the SPS and Machine Protection via Fast Position Interlocking
DESY Accelerator Physics SeminarFebruary, 9th 2010 3
1. CERN Accelerator Complex
2. Operational Experience with the LHC
3. Tune Resonance Phenomena in the SPS and Machine Protection via Fast Position Interlocking
DESY Accelerator Physics SeminarFebruary, 9th 2010 4
CERN
Mt. Blanc
Lake Geneva
CMS
Geneva
LHCb
ATLAS
ALICE
DESY Accelerator Physics SeminarFebruary, 9th 2010 5
CERN Accelerator Complex
DESY Accelerator Physics SeminarFebruary, 9th 2010 6
• Ring circumference: 26.7 km
• Collision Energy: 2 ∙ 7 TeV
• 4+2 Experiments: ATLAS, CMS, ALICE, LHCb andTOTEM, LHCf
Large Hadron Collider
DESY Accelerator Physics SeminarFebruary, 9th 2010 7
1. CERN Accelerator Complex
2. Operational Experience with the LHC
3. Tune Resonance Phenomena in the SPS and Machine Protection via Fast Position Interlocking
DESY Accelerator Physics SeminarFebruary, 9th 2010 8
• LHC incident
• LHC run 2009
• Plans for 2010
2. Operational Experience with the LHC
DESY Accelerator Physics SeminarFebruary, 9th 2010 9
LHC startup 2008
LHC startup: September 10th 2008
• Both beams around the ring (within few hours)
Following days:
• All base instrumentation operational (BPMs, BLMs, Tune, BCTs)
• Beam 2 captured by RF
• Beam lifetime > 1h
DESY Accelerator Physics SeminarFebruary, 9th 2010 10
September 19th Incident
Quadrupole-dipole interconnection (27R3)
DESY Accelerator Physics SeminarFebruary, 9th 2010 11
September 19th Incident
Quadrupole-dipole interconnection (27R3)
Vacuum chamber
Dipole Bus bar
DESY Accelerator Physics SeminarFebruary, 9th 2010 12
Bus Bar
DESY Accelerator Physics SeminarFebruary, 9th 2010 13
Bus Bar
bus U-profile bus
wedge
Solder
bus U-profile bus
wedge
Solder No solder
Good joint
Bad joint
DESY Accelerator Physics SeminarFebruary, 9th 2010 14
Event Sequence on Sept. 19th
• Last commissioning step of main dipole circuit in sector 34: ramp to 9.3 kA (5.5 TeV)
• At 8.7 kA electrical fault in bus bar between dipole and quadrupole
Local resistance: ~220 nW (nominal 0.35 nW)
• 400MJ out of 600MJ stored in the circuit were dissipated in cold-mass and electrical arcs
• 6 tons of helium were released
DESY Accelerator Physics SeminarFebruary, 9th 2010 15
LHC repairs in detail
14 quadrupolemagnets replaced
39 dipole magnets replaced
204 electrical inter-connections repaired
Over 4km of vacuum beam tube cleaned
New longitudinal restraining system for 50 quadrupoles
Almost 900 new helium pressure release ports
6500 new detectors and 250km cables for new Quench Protection System
DESY Accelerator Physics SeminarFebruary, 9th 2010 16
LHC run 2009
DESY Accelerator Physics SeminarFebruary, 9th 2010 17
Startup Nov. 20th 2009
Beam position
Also Day 1: Capture of both beams with RF
DESY Accelerator Physics SeminarFebruary, 9th 2010 18
Startup Nov. 20th 2009
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First Collisions
Day 4: First collisions at 2∙450 GeV
ATLAS CMS
DESY Accelerator Physics SeminarFebruary, 9th 2010 20
Ramp
Day 4: 1st Ramp to 560 GeV
Day 11: 3rd Ramp to 1.18 TeV
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3rd Ramp
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Tune = Number of betatron oscillations per machine revolution
Tune
S=0 Closed Orbit
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Tune = Number of betatron oscillations per machine revolution
Tune
S=0 Closed Orbit
DESY Accelerator Physics SeminarFebruary, 9th 2010 24
Tune = Number of betatron oscillations per machine revolution
Tune
S=0
QH ≈ 7.6
Closed Orbit
BetatronOscillation
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Tune = Number of betatron oscillations per machine revolution
Tune Resonance: m∙QH±n∙QV=k m, n, k = integer
m+n = order of resonance
Tune
S=0
QH ≈ 7.6
Closed Orbit
BetatronOscillation
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Ramp to 1.18 TeV
DESY Accelerator Physics SeminarFebruary, 9th 2010 27
CMS Solenoid
Day 10: Switching on CMS Solenoid.
Orbit difference with/without Solenoid on
Momentum change: dp/p = -0.1 ‰
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Tidal Effect on Energy
LHC measures influence of tidal forces 10 days after first beam
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Milestones in 2009 run
Date Day Achieved
Nov 20 1 Both beams circulating. Key beam instrumentation working.
Nov 23 4 First collisions at 450 GeV. First ramp (reached 560 GeV).
Nov 30 11 Ramp to 1.18 TeV.
Nov 30 11 Experiment solenoids on.
Dec 04 15 Aperture measurements finished. LHCb and ALICE dipoles on.
Dec 05 16 Machine protection (Injection, Beam dump, Collimators) ready for safe operation with pilots.
Dec 08 19 Ramp colliding bunches to 1.18 TeV
Dec 14 25 Collisions with STABLE BEAMS, 16 on 16 bunches at 450 GeV,Intensity > 1010 protons per bunch
Dec 16 27 Ramp 4 on 4 bunches to 1.18 TeV. Squeeze to β*=7 m.
DESY Accelerator Physics SeminarFebruary, 9th 2010 30
Plans for 2010
DESY Accelerator Physics SeminarFebruary, 9th 2010 31
Plans for 2010
Date Activity
Feb 16 Injection Test
Feb 22 Start recommissioning with Beam
End Feb Ramp to 3.5 TeV.
Beg. Mar Commission Squeeze
Mid Mar Stable, Save Beams at 3.5 TeV
Stepwise Increase Intensity, each step followed by extended running period (estimate: up to ≈7∙1013 protons during 2010)
Ramp to Higher Energies in 2013 (warm up of machine needed)
DESY Accelerator Physics SeminarFebruary, 9th 2010 32
1. CERN Accelerator Complex
2. Operational Experience with the LHC
3. Tune Resonance Phenomena in the SPS and Machine Protection via Fast Position Interlocking
DESY Accelerator Physics SeminarFebruary, 9th 2010 33
• Incident 27.06.2008
• Integer Tune resonances
• Orbit Resonance
• Dispersion Resonance
• Supersymmetric Resonances
• Machine Protection
3. Tune Resonance Phenomena in the SPS and Machine Protection via Fast Position Interlocking
DESY Accelerator Physics SeminarFebruary, 9th 2010 34
• Commissioned in 1976
• Ring circumference: 6.9 km
• Top Energy: 450 GeV
• Intensity: up to5∙1013 protons
• Beam Energy: up to 2.5 MJ
• Tevatron: 2 MJ, LHC (nominal) 362MJ
Super Proton Synchroton
Octupole
Sextupole
Correctors and BI
Quadrupole
4 Dipoles
DESY Accelerator Physics SeminarFebruary, 9th 2010 35
• Commissioned in 1976
• Ring circumference: 6.9 km
• Top Energy: 450 GeV
• Intensity: up to5∙1013 protons
• Beam Energy: up to 2.5 MJ
• Tevatron: 2 MJ, LHC (nominal) 362MJ
Super Proton Synchroton
Octupole
Sextupole
Correctors and BI
Quadrupole
4 Dipoles
DESY Accelerator Physics SeminarFebruary, 9th 2010 36
SPS Incident 27.06.2008
DESY Accelerator Physics SeminarFebruary, 9th 2010 37
SPS Incident June 27th 2008
Beam impact of high intensity beam
(about 3∙1013 protons @ 400 GeV)
DESY Accelerator Physics SeminarFebruary, 9th 2010 38
SPS Incident June 27th 2008
Beam impact of high intensity beam
(about 3∙1013 protons @ 400 GeV)
DESY Accelerator Physics SeminarFebruary, 9th 2010 39
Event Sequence on June 27th
• After injection of 2 high intensity batches a failure in the main timing system occurred
• The beam was accelerated to 400GeV but not extracted
• The magnets were ramped down again
• The tune shifted towards an integer tune resonance and the beam punctured the vacuum chamber in the vertical plane (dipole current corresponding to 399.05 GeV)
DESY Accelerator Physics SeminarFebruary, 9th 2010 40
SPS Incident June 27th 2008
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Integer Tune Resonance
DESY Accelerator Physics SeminarFebruary, 9th 2010 42
Integer Tune Resonance
• Influence of dipolar error on Closed Orbit:
(e.g. quadrupole misalignments)
s
sdQssssFQ
ssx ))()(cos()()(
)sin(2
)()(
DESY Accelerator Physics SeminarFebruary, 9th 2010 43
Integer Tune Resonance
• Influence of dipolar error on Closed Orbit:
(e.g. quadrupole misalignments)
s
sdQssssFQ
ssx ))()(cos()()(
)sin(2
)()(
Beta functionBetatron phase
Resonance conditionError function Tune
DESY Accelerator Physics SeminarFebruary, 9th 2010 44
Integer Tune Resonance
• Influence of dipolar error on Closed Orbit:
(e.g. quadrupole misalignments)
• QH, QV = integer => diverging closed orbit
s
sdQssssFQ
ssx ))()(cos()()(
)sin(2
)()(
Beta functionBetatron phase
Resonance conditionError function Tune
DESY Accelerator Physics SeminarFebruary, 9th 2010 45
Turn-by-Turn Position
Linear Decrease of Horizontal Tune
DESY Accelerator Physics SeminarFebruary, 9th 2010 46
Orbit Resonances
0
2
4
6
8
10
23.5 24.0 24.5 25.0 25.5 26.0 26.5
Ho
rizo
nta
l RM
S cl
ose
d o
rbit
[m
m]
Horizontal Tune
Horizontal RMS closed orbit
Measurement
Simulation
NominalQH=26.13
DESY Accelerator Physics SeminarFebruary, 9th 2010 47
Turn-by-Turn Position
Linear Decrease of Horizontal Tune
DESY Accelerator Physics SeminarFebruary, 9th 2010 48
• Dispersion:
(generated by dipole magnets, transforms like orbit)
Dispersion Resonance
p
psDsx
)()(
DESY Accelerator Physics SeminarFebruary, 9th 2010 49
• Dispersion:
(generated by dipole magnets, transforms like orbit)
Error function
Dispersion Resonance
Beta functionBetatron phase
Resonance condition
p
psDsx
)()(
s
sdQssssFQ
ssx ))()(cos()()(
)sin(2
)()(
Tune
DESY Accelerator Physics SeminarFebruary, 9th 2010 50
• Dispersion:
(generated by dipole magnets, transforms like orbit)
Error function
Dispersion Resonance
Beta functionBetatron phase
Resonance condition
p
psDsx
)()(
s
sdQssssFQ
ssx ))()(cos()()(
)sin(2
)()(
D
)(
1
s
Bending radiusTune
DESY Accelerator Physics SeminarFebruary, 9th 2010 51
• Dispersion:
(generated by dipole magnets, transforms like orbit)
• QH, QV = integer => diverging dispersion
Error function
Dispersion Resonance
Beta functionBetatron phase
Resonance condition
p
psDsx
)()(
s
sdQssssFQ
ssx ))()(cos()()(
)sin(2
)()(
D
)(
1
s
Bending radiusTune
DESY Accelerator Physics SeminarFebruary, 9th 2010 52
Dispersion Resonance
DESY Accelerator Physics SeminarFebruary, 9th 2010 53
Dispersion Resonance
0
5
10
15
20
25
23.5 24.0 24.5 25.0 25.5 26.0 26.5
Ho
rizo
nta
l RM
S D
isp
ers
ion
[m
]
Horizontal Tune
Horizontal RMS Dispersion
MeasurementMeasurement (Shifted Tune)Simulation
NominalQH=26.13
DESY Accelerator Physics SeminarFebruary, 9th 2010 54
SPS: Supersymmetry of 6
Supersymmetric Resonances
DESY Accelerator Physics SeminarFebruary, 9th 2010 55
SPS: Supersymmetry of 6
Supersymmetric Resonances
1
2 3
4
56
DESY Accelerator Physics SeminarFebruary, 9th 2010 56
Supersymmetric Resonances
1
2 3
4
56
SPS: Supersymmetry of 6
DESY Accelerator Physics SeminarFebruary, 9th 2010 57
Supersymmetric Resonances
1
2 3
4
56
SPS: Supersymmetry of 6
• When Tune is multiple of 6:
Extreme Dispersion Resonance
• Dipole fields are super-symmetric
Integer Orbit Resonance
• Dipole errors are randomly distributed (no strong supersymmetry)
DESY Accelerator Physics SeminarFebruary, 9th 2010 58
Machine Protection
DESY Accelerator Physics SeminarFebruary, 9th 2010 59
Power Converter Interlock
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Fast Position Interlock
• Original Design:
• 6 stripline coupler BPMs
• new Hardware using logarithmic amplifiers (large dynamic range)
• Turn-by-Turn Acquisition and Interlock Processing via FPGA
• Post Mortem Acquisition (1024 turns)
DESY Accelerator Physics SeminarFebruary, 9th 2010 61
Acquisition Commissioning
y = 0.60x - 0.79
y = 0.59x - 0.39
-8
-6
-4
-2
0
2
4
6
8
-8 -6 -4 -2 0 2 4 6 8
vert
ical
po
siti
on
me
asu
red
by
new
HW
[m
m]
vertical position measured by MOPOS [mm]
New Hardware vs. Traditional Hardware(vertical orbit bump)
BPCE.618 V-position @ injection
BPCE.618 V-position @ 49 GeV
07 - 09.11.2009, CNGS beam@ injection: 14GeV, 2∙1013 p
@ 49GeV: 4∙1013 p
DESY Accelerator Physics SeminarFebruary, 9th 2010 62
Acquisition Commissioning
Consistency Check:Vertical 3π orbit bump at BPCE 618
DESY Accelerator Physics SeminarFebruary, 9th 2010 63
Acquisition Commissioning
y = 0.97x - 0.14y = 1.06x - 0.08
y = 1.76x - 0.07
-6
-4
-2
0
2
4
6
8
-4 -3 -2 -1 0 1 2 3 4
vert
ical
po
siti
on
me
asu
red
/tri
mm
ed
[m
m]
fitted bump amplitude @ BPCE.618.V [mm]
New Hardware vs. Traditional Hardware(3π vertical orbit bump)
Nominal Trim
BPCE.618.V new hardware
BPCE.618.V MOPOS
12.11.2009, CNGS beam14GeV, 2∙1013 p
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• Compare current position with moving average of last 100 turns
• Interlock if difference larger 3mm
• Outlier detection
Interlock Algorithm
DESY Accelerator Physics SeminarFebruary, 9th 2010 65
Interlock Algorithm
• Compare current position with moving average of last 100 turns
• Interlock if difference larger 3mm
• Outlier detection
Problem: Injection Oscillations
DESY Accelerator Physics SeminarFebruary, 9th 2010 66
Interlock Algorithm
• Compare current position with moving average of last 100 turns
• Interlock if difference larger 3mm
• Outlier detection
Problem: Injection Oscillations
• Probable solution:
(Time dependent) Low pass filter
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Fast Position Interlock
DESY Accelerator Physics SeminarFebruary, 9th 2010 68
Fast Position Interlock
Offline test: 428/428 tune resonances triggered, 0/554 normal orbits triggered
in-situ tests continue next week
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Summary
• (Integer) Tune Resonance are a challenging Machine Protection Issue
• (cp. complete beam loss in 3 turns)
• Protection with Turn-by-Turn Position Interlock
• When you are fast enough you can cross every resonance
• Be aware of Supersymmetric Tune Resonances
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Thank you
for your Attention
Tobias Baer
CERN BE/OP
Office: +41 22 76 75379
DESY Accelerator Physics SeminarFebruary, 9th 2010 71
Backup slides
DESY Accelerator Physics SeminarFebruary, 9th 2010 72
LHC Main Dipole Circuit
Global protection of the bus-bar and bus-bar joints (splices) between magnets.
Protection threshold 1 V (160 V inductive voltage during ramp).
Bus-bar must cope with 100 second discharge time of circuit.
Local (quench) protection of each magnet
DESY Accelerator Physics SeminarFebruary, 9th 2010 73
Beam Screen Contamination
Beam Screen (BS) : The red color is characteristic of a clean copper
surface
BS with some contamination by super-isolation (MLI multi layer
insulation)
BS with soot contamination. The grey color varies depending on the thickness of the soot, from grey to
dark.
Beam screen with clean Copper surface
contaminated by super-isolation
contaminated with soot
60% of the chambers 20% of the chambers
Beam Screen (BS) : The red color is characteristic of a clean copper
surface
BS with some contamination by super-isolation (MLI multi layer
insulation)
BS with soot contamination. The grey color varies depending on the thickness of the soot, from grey to
dark.
Beam Screen (BS) : The red color is characteristic of a clean copper
surface
BS with some contamination by super-isolation (MLI multi layer
insulation)
BS with soot contamination. The grey color varies depending on the thickness of the soot, from grey to
dark.
DESY Accelerator Physics SeminarFebruary, 9th 2010 74
Cleaning of Beam Screen
Up to 50 passages in each direction with wet foam (alcohol)
Up to 15 passages with dry foam
DESY Accelerator Physics SeminarFebruary, 9th 2010 75
Triplet Movement
12µm triplet misalignment => beam oscillation amplitude 0.3mm (in arc)
7.454
7.456
7.458
7.460
7.462
7.464
7.466
7.468
7.470
20:30 21:00 21:30 22:00 22:30 23:00 23:30 0:00
po
siti
on
[m
m]
time (UTC)
Haiti Earthquake (12.01.2010) measured by LHC hydrostatic leveling system
GISB.UX851R.HLS_LO:HEIGHT_MM
21:53 Earthquake
DESY Accelerator Physics SeminarFebruary, 9th 2010 76
Triplet Movement
-0.800
-0.600
-0.400
-0.200
0.000
0.200
0.400
0.600
0.800
1.000
vert
ical
po
siti
on
[m
m]
s [m]
12µm Misalignment of MQXB.A2R5
DESY Accelerator Physics SeminarFebruary, 9th 2010 77
Hump and UPS
Hump: Fast frequency shifting oscillation Time resolved Hump structure
with mean drifting slowly between0.25 and 0.32
courtesy of Ralph Steinhagen
DESY Accelerator Physics SeminarFebruary, 9th 2010 78
Dispersion Resonance
DESY Accelerator Physics SeminarFebruary, 9th 2010 79
Dispersion Resonance
DESY Accelerator Physics SeminarFebruary, 9th 2010 80
Dispersion Resonance
DESY Accelerator Physics SeminarFebruary, 9th 2010 81
Dispersion Resonance
DESY Accelerator Physics SeminarFebruary, 9th 2010 82
FMCM
Recombination Dipole RD1 OFF, FMCM active
DESY Accelerator Physics SeminarFebruary, 9th 2010 83
FMCM
Recombination Dipole RD1 OFF, FMCM masked (inactive)
83
orbit starts to change 270 turns = 23.9 ms before beam dump
00:21:29.4200orbit start to change 00:21:29.3961
FMCM masked trigger 00:21:29.378
beam losses start at00:21:29.4020
courtesy of Rudiger Schmidt
DESY Accelerator Physics SeminarFebruary, 9th 2010 84
Beam Losses
Recombination Dipole RD1 OFF, FMCM masked (inactive)
courtesy of Rudiger Schmidt
beam losses start at00:21:29.402
DESY Accelerator Physics SeminarFebruary, 9th 2010 85
Power Converter
Recombination Dipole RD1 OFF, FMCM masked (inactive)
DESY Accelerator Physics SeminarFebruary, 9th 2010 86
Power Converter
Recombination Dipole RD1 OFF, FMCM masked (inactive)
BLM trigger: 00:21:29.420
dI = 0.69 A (1.6%)Inom = 43.17 AIdump = 42.42 A
orbit starts to change 00:21:29.396
FMCM trigger
dI=0.025%
courtesy of Rudiger Schmidt
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DESY Accelerator Physics SeminarFebruary, 9th 2010 88
DESY Accelerator Physics SeminarFebruary, 9th 2010 89
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