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