LHC
Commissioning
R. Giachino

R. Giachino

CERN

CERN

WAO 2010

1Outline

1.
2.
3.
4.
5.

R. Giachino

Introduction
Starting the LHC
Sector 3-4 Incident & Repair
LHC Beam Operation
Conclusions

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2CERN Accelerator ComplexCERN
Large Hadron Collider(LHC)

Super Proton Synchrotron(SPS)

Proton Synchrotron(PS)
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3CERN Accelerator ComplexCERN

CMS

LHC-b

ALICE

ATLAS

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4ATLAS

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5CMS

6
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6LHCb

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7ALICE

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8The 15m LHC Cryodipole

R. Giachino• 1232 Dipole Magnets•2-in-1 Design, Two 56mm Beam Tubes•B-Field 8.3 Tesla, 11.8kA , 1.9K, Super fluid Helium
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9Cryogenic Plant“Cryo Maintain” – Allowing Circulating Beams 90.4% Available

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10

th
Day One – September 10 2008

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th
Day One – September 10 2008

Single bunch of protons 3 x 109
Beam 1
1. Injected Point 2
2. Threaded around machine in 1 hour
3. Trajectory steering gave 2 or 3 turns
Beam 2
1. Injected Point 8
2. Threaded around machine in 1.5 hours
3. Trajectory steering gave 2 or 3 turns
4. Q and Q’ tuning gave several hundred turns
No Major Magnetic Problem

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No Major Obstacle

CERN12thDay Nine – September 19 2008

On Day One not all circuits had been commissioned
Final Commissioning Main Dipole Circuit 34

R. Giachino•Electrical Fault at 5.2 TeV in dipole bus bar, between quadrupole and dipole
Post-Analysis: R = 220 nΩ, nominal = 0.35nΩ•

Electrical Arc developed and punctured helium enclosure
Post-Analysis: 400 MJ dissipated in cold-mass and arcing•Helium Release into the insulating vacuum
Post-Analysis: Pressure wave caused most damage

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Electrical Fault and Arc

Vacuum Chamber
Dipole bus bar

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Pressure wave
QV

QV
Q

SV
D

D

DCold-mass
Vacuum vessel
Line E
Cold support post
Warm Jack
Compensator/Bellows
Vacuum barrier

Q

QV
D

D

DPT
Q

SV
D

DDQ

QV
D

D

D

QV
Q

1. Pressure Wave propagates inside insulation Vacuum enclosure
2. Rapid Pressure Rise
Self actuating relief valves could not handle pressure
Design: 2Kg He/s Incident: ~20 kg He/s
3. Forces on the vacuum barriers (every second cell)
Design: 1.5 bar Incident: ~8 bar•••

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Several Quadrupoles Displaced by ~50 cm
Cryogenic line connections damaged
Vacuum to atmospheric pressure
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Incident location

Dipole bus bar

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Collateral Damage
Quadrupole-dipole interconnection

Quadrupole support
Main Damage Area: 700m•••

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39 dipoles and 14 quadrupoles effected
moved to surface:
37 replaced and 16 repaired

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Ideal 13 kA Connection Scheme
Superconducting Cable
Tin – Silver Foils

Cross Section View
Longditudinal View – filled with Solder
CopperStabiliser

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Superconducting
Cable

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Observed Interconnections

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LHC repair and consolidation
14 quadrupole
magnets replaced

New longitudinal restraining
system for 50 quadrupoles

39 dipole magnets
replaced

204 electrical interconnections repaired

Almost 900 new heliumpressure release ports

Over 4km of vacuum
beam tube cleaned

6500 new detectors and 250km cables
for new Quench Protection System toprotect from busbar quenches

Collateral damage mitigationR. Giachino

CERN20Machine wide activities 2008/9
Sector 34 repair

Q4 2008

Q1 2009

Restart

Q2 2009

Q3 2009

Q4 2009– Calorimetric & electrical splice measurements at cold (measuring nΩ) Q4 2008
• Had to warm up sectors 1-2 6-7 to exchange magnets (and 5-6 for other reasons)– Electrical stabilizer measurements at warm or 80K (measuring µΩ) Q1 - Q3 2009
– Major new protection system based on electrical measurements Q1 – Q4 2009 (nQPS)– Pressure relief valves installed where possible Q1 – Q3 2009 (dipoles have to be warm)– floor anchors reinforced Q1 – Q3 2009
Q4 2008

Q1 2009

Q2 2009

Q3 2009

Q4 200912

Cold

Cold  Warm

Warm

Warm  Cold

Cold

23

< 100K< 100K< 100K  Cold

Cold  80K  Cold

Cold

34

Warm

Warm

Warm

Warm  Cold

Cold

45

< 100K< 100K80K  Warm

Warm  Cold

Cold

56

Cold

Cold  Warm

Warm

Warm  Cold

Cold

67

Cold

Cold  Warm

Warm

Warm  Cold

Cold

78

Cold

< 100K< 100K  80K

80K  Cold

Cold

81

Cold

< 100K< 100K  80K80K  Cold

Cold

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th20 November 2009 LHC was back14 months to repair, consolidate and re-commission all elements• Energy Limit 1.2 TeV in 2009 – bringing bus-bar quench protection system online
20th November – Circulating beams again!

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Diagnostics Available on Day Zero
Some examples…

•RF / Capture•Tune Measurements•Orbit Measurements•Wire Scanners•Machine Protection

And more…
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2009 Beam Operation Milestones
20th November
23rd November
29th November
6th December
8th December••••

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Day 0Day 3Day 9Day 16Day 18

Both Beams Circulating after 6 hours
First pilot collisions at 450 GeV
Beams ramped to 1.18 TeV
Stable Collisions at 450 GeV for experiments
First collisions at 1.18 TeVCommissioned at a forced pace – aim to check as much as possible
Uptime 60% - Very good at this stage
Most optimistic dreams came true
A touch of modesty
Stored energy did not exceed 30 kJ – 0.01% of nominal

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2010-2011 planning
Jan-Feb 2010: commissioning of LHC circuits for 3.5 TeV operation.
Beam operation 2010:•Start-up with beam.
End February•
Consolidation at 450 GeV (optics…).
•Ramp to 3.5 TeV.
End March•
Low intensity collisions at 3.5 TeV.
•Interaction spot size squeezing.
TodayApril•
Low intensity collisions at 3.5 TeV squeezed.
•Stepwise (factor 2-4) increase of intensity to 1-2 MJ/ beam
Summer
•Switch from individual bunches to bunch train (50 ns).
•…
•
Lead ion run
November

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3.5 TeV collisions

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SummaryThe electrical incident revealed quality issues of the bus-bar joints.
14 months of repair and re-commissioning.
New diagnostics for online monitoring and protection of all joints.

Eradication of joint issues requires a complete warm-up and long
shutdown.

The LHC beam energy will be limited to 3.5 TeV in 2010/2011.
Long shutdown in 2012 to prepare LHC for 7 TeV / beam.

Very successful beam commissioning to 1.2 & 3.5 TeV.
LHC is reproducible.
Collisions at 3.5 TeV established.
Increase stepwise intensity through the year.
Ready to operate 18 months at 3.5 TeV

But the real beam challenges are ahead of us !

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Collisions 1.2 TeV

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Food for thought – Tune Spectra

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