status of the lhc machine
DESCRIPTION
Status of the LHC machine. W. Venturini Delsolaro for the LHC team IHEP 19.10.2010. OUTLINE. Nah ist Und schwer zu fassen der Gott. Wo aber Gefahr ist, wächst Das Rettende auch. Friedrich Hölderlin, 1802 Targets for 2010 and commissioning strategy Beam operation in 2010 - PowerPoint PPT PresentationTRANSCRIPT
Status of the LHC machine
W. Venturini Delsolaro for the LHC teamIHEP 19.10.2010
OUTLINE
Nah istUnd schwer zu fassen der Gott.
Wo aber Gefahr ist, wächstDas Rettende auch.
Friedrich Hölderlin, 1802
Targets for 2010 and commissioning strategyBeam operation in 2010Problems encountered and how we (almost) overcame themOverlook on 2011 and beyond
LHC nominal parameters
3
Nominal settingsBeam energy (TeV) 7.0Number of particles per bunch 1.15 1011
Number of bunches per beam 2808Crossing angle (rad) 285Norm transverse emittance (m rad) 3.75Bunch length (cm) 7.55Beta function at IP 1, 2, 5, 8 (m) 0.55,10,0.55,10
Derived parametersLuminosity in IP 1 & 5 (cm-2 s-1) 1034 Luminosity in IP 2 & 8 (cm-2 s-1)* ~5 1032
Transverse beam size at IP 1 & 5 (m) 16.7Transverse beam size at IP 2 & 8 (m) 70.9Stored energy per beam (MJ) 362
* Luminosity in IP 2 and 8 optimized as needed
Instantaneous luminosity
4
• Nearly all the parameters are variable (and not independent)– Number of bunches per beam kb
– Number of particles per bunch – Normalized emittance n
– Relativistic factor (E/m0) – Beta function at the IP *
– Crossing angle factor F• Full crossing angle c
• Bunch length z
• Transverse beam size at the IP *
FfkNFfkNLn
b
yx
b*
22
44
2
*21/1
zcF
Interaction Region
Energy
Total IntensityBeam
Brightness
Bunch Intensity N already nominal!
normalized emittance << nominal!
Evolution of target energy
5
2002-20077 TeV
Summer 20085 TeV
Summer 20093.5 TeV
October 2009
450 GeV
Re training
Stabilizers
nQPS 2 kA
6 kA
9 kA
When Why
12 kA
Late 2008 SC splices
1.18 TeV
Design
2010Fix nQPSTest 6kA
3.5 TeV
Quench Protection System upgrade
We Run at 3.5 TeV to avoid “Silent killers” Bad surprise after gamma-ray imaging of the joints
Void is present in bus extremities because SnAg flowed out during soldering of the joint
LHC Intensity limits 2010 2011
8
Fix Imax to 6 1013 protons per beam at 3.5TeV(about 20% nominal intensity)
30MJ stored beam energy
0.2%/s assumed• First stage to allow 40% of nominal intensity
at 7 TeV• Assumptions
• LHC lifetimes and loss rates• 0.1%/s assumed (0.2h lifetime)• Ideal cleaning
• Imperfections bring this down• Deformed jaws• Tilt & offset & gap errors• Machine alignment
• Machine stability• Tight settings a challenge early• Intermediate settings make use
of aperture to relax tolerances
• Staged collimation system
Lower energy means bigger beamsLess aperture margin around the IPβ* has to be increased at lower energy
> 150 bunches requires crossing angleRequires more apertureHigher β* again helps
Targets for 3.5 TeV2 m no crossing angle3 m with crossing angle
9
β* and F in 2010-2011
n
Operation before splice consolidation
Repair of Sector 34 1.18TeV
nQPS6kA
3.5 TeVIsafe < I < 0.2 Inom
β* > 2 mIons
3.5 TeV~ 0.2 Inom
β* ~ 2 mIons
2009 2010 2011
No Beam B Beam Beam
Energy limited to 3.5 TeV2010
Intensity carefully increased to collimation limitβ* pushed as low as possibleTarget luminosity 1032 cm-2s-1
2011Run at established limitsTarget integrated luminosity 1 fb-1
40% efficiency for physics → 106 seconds collisions per month
106 seconds @ <L> of 1032 cm-2 s-1 → 100 pb-1
Energy TeV 3.50 3.50 3.50 3.50Bunch intensity 1.E+10 10.0 10.0 10.0 10.0Bunches per beam 4 24 432 792Emittance µm 3.75 3.75 3.75 3.75β* m 3.50 3.50 3.50 3.50 Luminosity 1 and 5 cm-2 s-1 1.0E+30 6.1E+30 1.1E+32 2.0E+32Total inel X section cm2 6.0E-26 6.0E-26 6.0E-26 6.0E-26Event rate Hz 6.1E+04 3.7E+05 6.5E+06 1.2E+07Event rate / Xing Hz 1.4 1.4 1.3 1.3 Protons 4.0E+11 2.4E+12 4.3E+13 7.9E+13% nominal 0.1 0.7 13.4 24.5Current mA 0.7 4.3 77.7 142.5Stored energy MJ 0.2 1.3 24.2 44.4Beam size 1 and 5 um 59.3 59.3 59.3 59.3
At whatever energyCorrect everything we can with safe beamsThen establish referencesThen set up protection devicesThen increase intensity incrementally
Low bunch currents, increase kbIncrease bunch currentHigh bunch current, low kb, same total currentNominal bunch currents, increase kbOnce kb > 50 or so, need bunch trains
At each stage, re-qualify machine protection systems
11
Commissioning strategy
Some numbersWhat Limit CommentPilot Single bunch of 5 109
protonsQuench limit
Safe beam
1012 protons at 450 GeV Damage limit
Energy Safe beam
Scales with 1/E1.7
0.45 1.00E+121.18 1.94E+113.5 3.06E+107 9.41E+09
Machine protection
MP phase 1: low intensity MP commissioning. Commissioning of the protection systems.Low intensity single bunch commissioning of the systems, including beam tests (manually triggered failures).
MP phase 2: MP running in with gradual intensity increase.
Intensity increase in steps, factor 2 – 4, up to ~ MJ stored energy.Stability run of a few weeks around 1-3 MJ.
MP Phase 3: intensity increase to 10’s MJ regime.Intensity increase in steps of 2-3 MJ (1 TEVATRON beam).Initially planned one step every 1-2 weeks. With the good MPS performance, agreed to reduce the step to:
3 fills and 20 hours of stable beams to monitor and cope with the new phenomena arising when increasing the number of bunches
Good setup - hierarchy respected
13
The collimator hierarchy is verified with dedicated loss maps induced by artificially high loss rates: record beam losses around the ring while crossing betatron resonances.
IP4 IP5 IP6 IP7 IP8
β cle
aning
Δp/p
clea
ning
Dump
TCTs
TCTsTC
TsIP1 IP2 IP3
Beam 1
IP7
TCPs
TCSG
s
TCLA
s
Normal cond. magnet cleaning insertion
Milestones reached 2010 (i)
14
Date Achieved
Feb 28 Restart with beam.
Mar 12 Ramp to 1.18 TeV.
Mar 19 Ramp to 3.5 TeV.
Mar 30 First collisions at 7 TeV centre of mass. Luminosity ~ 2 1027 cm-2 s-1
Apr 01 Start squeeze commissioning.
Regular physics runs2 on 2 bunches of 1010
Un-squeezed1 colliding pairs per experimentRates around 100Hz
Apr 07 Squeeze to 2 m in points 1 and 5.
Apr 09 Single nominal bunch of 1.1 1011 stable at 450GeV.
Apr 16 Squeeze to 2m in all points
April 24 First stable beams at 7 TeV, 3 on 3, squeeze to 2m.
Luminosity ~ 2 1028cm-2 s-
1
May Increase bunch intensity to 2 1010, Increase kb. Regular physics runs
Milestones reached 2010 (Ii)
May 24 13 on 13, 8 colliding pairs per experiment. Luminosity ~ 3 1029cm-2 s-1
June Increase bunch intensity to nominal, squeeze to 3.5m.
No physics !
June 25 First stable beams at 7 TeV, 3 on 3 nominal bunch.
Luminosity ~ 5 1029cm-2 s-1
July 15 13 on 13, 8 colliding pairs per experiment, 9 1010 / bunch
Luminosity ~ 1.5 1030cm-2 s-1
July 30 25 on 25, 16 colliding pairs per experiment, 9 1010 / bunch
Luminosity ~ 3 1030cm-2 s-1
Aug 19 48 on 48, 36 colliding pairs 1 5 and 8 (< in 2), 9 1010 / bunch
Luminosity ~ 6 1030cm-2 s-1
Aug Stable running period to consolidate operation and MP
~2 MJ per beam
4-10 Sept Commissioning of 10A/s ramp, transverse FB, Xing angle studies
No physics !
10-22 Sept Commissioning of bunch trains, setting up of protection devices
No physics !
23Sept-14 Oct
Stable beams with increasing kb (56104 152 200 248 ….)
~15 MJ per beam, L ~ 1032
cm-2 s-1
fill 1418, <n> ~ 1011 , kb=248
Peak Luminosity 1032 cm-2s-1
Integrated luminosity over the fill > 2.4 (pb)^-1
Integrated Luminosity delivered So far
Status of the machine in short
Overall good availability (special mention for Cryogenics)Key systems performing well, still some cleanup
InjectionBeam dumping CollimationBeam interlocking system (Machine Protection)RF (power, longitudinal blow up and transverse feedback…
Magnetically well understood and reproducibleFeedbacks on orbit and tunes operational through all cycleAperture is even better than expectedSmall emittances, nominal bunch intensitiesExcellent single beam lifetimes (vacuum, RF, optics)Beam-beam is there but well under control (transverse FB, crossing angles)
Optics stability
The hump mystery
20
Broad frequency “hump” driven beam excitation → emittance blow-up
Vertical plane, worse for beam 2
Actually a fast frequency shifting oscillation with slowly drifting mean
Many sources excluded, but culprit still out there
Ramp rate
21
At the start of the run the ramp rate had to be limited to 2 A/s (1.2 GeV/s) for magnet protection reasons.o Ramp duration 0.45-3.5 TeV: 46 minutes
Since mid-July the rate for down-ramps and magnet pre-cycles (magnetic history reset) was increased to nominal value of 10 A/s (6 GeV/s).
Ramp speed with beam now to 10 A/s (6 GeV/s).o Pure ramp duration 0.45-3.5 TeV: 16 minutes.
2 A/s 10 A/s
450 GeV
3500 GeV
Dynamic magnetic effects
Orbit, Q and Q’ decay and snapback (both on flat bottom and on flat top) Corrections “feed forwarded” in the operational cycle
B1 horizontal B1 vertical
Q’ during injection, ramp and flat top
Feedbacks on orbit and tunes
Evidence of Beam-beam
Coherent beam-beam instabilities observed in JulyStabilized first with Octupoles and then with transverse FB
Transverse feedback
Injection oscillations, dampers off
Injection oscillations, dampers on
Lifetime when Reducing Crossing Angle
3 batches of 8 bunches each, spacing 150 ns up to 6 parasitic interactions per bunch
100
rad170
100 mrad
80 r
ad70
rad
60 r
ad50
rad
40 r
ad30
rad
20 r
ad
90 r
ad
Minimum required X-ing angle is ~100 rad in 2010
Aperture with crossing angle on
With the 170 μrad (half) crossing angle, the on-momentum aperture in terms of nominal sigma is between 12.5 and 14.0 sigma for the two planes and two beams Predicted 8.4 sigma in the triplet, but no aperture limit in the triplet was found with beam up to at least 13 sigmaOrbit and mechanical tolerances much better than anticipated
Some issues increasing total intensity
Tune measurement at high beam currents solved
Before After change of FE
Beam driven Vacuum activity in IR
Improves with time spent at same intensity and longitudinal structure. Solenoids were installed and gave indications that some of this is driven by e- cloud
FAST losses bypassing the collimation (UFO)
Arc and DS BLM threshold increased by a factor 3. Seems to work with 248 bunches
Schedule – rest of 2010
32
Early Heavy Ion Run Parameters
33
Early (2010/11)(3.5 Z TeV)
Nominal(7 TeV)
√s per nucleon TeV 1.38 5.5Initial Luminosity (L0) cm-2s-1 ~1025 1027
Number of bunches 62 592Bunch spacing ns 1350 99.8* m 3.5 0.5Pb ions/bunch 7x107 7x107
Transverse norm. emittance m 1.5 1.5Luminosity half life (1,2,3 expts.) h IBS=7-30 8, 4.5, 3
Initial interaction rate: 100 Hz, ~108 interaction/106s (~1 month)
Possible performance improvements in 2011being (carefully) considered
Run at higher N/ε?Interesting beam physics: where is the real limit?Increase bunch intensityDecrease transverse emittance furtherMachine protection implications to be assessed
Run at higher energy…waking up the dragon? Risk assessment to be redone after experience with beam in 2010No beam induced quenches so far, better knowledge of quench limits (from tests with beam)RRR measurements Quench propagation measurements
2011 Q1&2
35
2011 Q3&4
36
The 10 year technical Plan