1. Status of the LHC machine W. Venturini Delsolaro for the LHC team IHEP 19.10.2010

2. 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 Problems encountered and how we (almost) overcame them Overlook on 2011 and beyond

3. LHC nominal parameters 3 Nominal settings Beam energy (TeV)7.0 Number of particles per bunch1.15 10 11 Number of bunches per beam2808 Crossing angle (  rad) 285 Norm transverse emittance (  m rad) 3.75 Bunch length (cm)7.55 Beta function at IP 1, 2, 5, 8 (m)0.55,10,0.55,10 Derived parameters Luminosity in IP 1 & 5 (cm -2 s -1 )10 34 Luminosity in IP 2 & 8 (cm -2 s -1 )*~5 10 32 Transverse beam size at IP 1 & 5 (  m) 16.7 Transverse beam size at IP 2 & 8 (  m) 70.9 Stored energy per beam (MJ)362 * Luminosity in IP 2 and 8 optimized as needed

4. Instantaneous luminosity 4 Nearly all the parameters are variable (and not independent) – Number of bunches per beamk b – Number of particles per bunch  – Normalized emittance  n – Relativistic factor (E/m 0 )  – Beta function at the IP  * – Crossing angle factorF Full crossing angle  c Bunch length  z Transverse beam size at the IP  * Interaction Region Energy Total Intensity Beam Brightness Bunch Intensity N already nominal! normalized emittance << nominal!

5. Evolution of target energy 5 2002-2007 7 TeV Summer 20085 TeV Summer 2009 3.5 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 nQPS Test 6kA 3.5 TeV

6. Quench Protection System upgrade

7. 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

8. LHC Intensity limits 2010 2011 8 Fix I max to 6 10 13 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

9. Lower energy means bigger beams Less aperture margin around the IP β* has to be increased at lower energy > 150 bunches requires crossing angle Requires more aperture Higher β* again helps Targets for 3.5 TeV 2 m no crossing angle 3 m with crossing angle 9 β * and F in 2010-2011

10. Operation before splice consolidation Repair of Sector 34 1.18 TeV nQPS 6kA 3.5 TeV I safe < I < 0.2 I nom β* > 2 m Ions 3.5 TeV ~ 0.2 I nom β* ~ 2 m Ions 200920102011 No BeamBBeam Energy limited to 3.5 TeV 2010 Intensity carefully increased to collimation limit β* pushed as low as possible Target luminosity 10 32 cm -2 s -1 2011 Run at established limits Target integrated luminosity 1 fb -1 40% efficiency for physics → 10 6 seconds collisions per month 10 6 seconds @ of 10 32 cm -2 s -1 → 100 pb -1 EnergyTeV3.50 Bunch intensity1.E+1010.0 Bunches per beam 424432792 Emittance µmµm 3.75 β*β* m3.50 Luminosity 1 and 5cm-2 s-11.0E+306.1E+301.1E+322.0E+32 Total inel X sectioncm26.0E-26 Event rateHz6.1E+043.7E+056.5E+061.2E+07 Event rate / XingHz1.4 1.3 Protons 4.0E+112.4E+124.3E+137.9E+13 % nominal 0.10.713.424.5 CurrentmA0.74.377.7142.5 Stored energyMJ0.21.324.244.4 Beam size 1 and 5um59.3

11. At whatever energy Correct everything we can with safe beams Then establish references Then set up protection devices Then increase intensity incrementally Low bunch currents, increase k b Increase bunch current High bunch current, low k b, same total current Nominal bunch currents, increase k b Once k b > 50 or so, need bunch trains At each stage, re-qualify machine protection systems 11 Commissioning strategy Some numbers WhatLimitComment PilotSingle bunch of 5 10 9 protonsQuench limit Safe beam10 12 protons at 450 GeVDamage limit EnergySafe beam Scales with 1/E 1.7 0.451.00E+12 1.181.94E+11 3.53.06E+10 79.41E+09

12. 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

13. 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. IP4IP5IP6IP7IP8 β cleaning Δp/p cleaning Dump TCTs IP1IP2IP3 Beam 1 IP7 TCPs TCSGs TCLAs Normal cond. magnet cleaning insertion

14. Milestones reached 2010 (i) 14 DateAchieved Feb 28Restart with beam. Mar 12Ramp to 1.18 TeV. Mar 19Ramp to 3.5 TeV. Mar 30First collisions at 7 TeV centre of mass.Luminosity ~ 2 10 27 cm -2 s -1 Apr 01Start squeeze commissioning. Regular physics runs 2 on 2 bunches of 10 10 Un-squeezed 1 colliding pairs per experiment Rates around 100Hz Apr 07Squeeze to 2 m in points 1 and 5. Apr 09Single nominal bunch of 1.1 1011 stable at 450GeV. Apr 16Squeeze to 2m in all points April 24First stable beams at 7 TeV, 3 on 3, squeeze to 2m.Luminosity ~ 2 10 28 cm -2 s -1 MayIncrease bunch intensity to 2 10 10, Increase k b. Regular physics runs

15. Milestones reached 2010 (Ii) May 2413 on 13, 8 colliding pairs per experiment.Luminosity ~ 3 10 29 cm -2 s -1 JuneIncrease bunch intensity to nominal, squeeze to 3.5m.No physics ! June 25First stable beams at 7 TeV, 3 on 3 nominal bunch.Luminosity ~ 5 10 29 cm -2 s -1 July 1513 on 13, 8 colliding pairs per experiment, 9 10 10 / bunch Luminosity ~ 1.5 10 30 cm -2 s -1 July 3025 on 25, 16 colliding pairs per experiment, 9 10 10 / bunch Luminosity ~ 3 10 30 cm -2 s -1 Aug 1948 on 48, 36 colliding pairs 1 5 and 8 (< in 2), 9 10 10 / bunch Luminosity ~ 6 10 30 cm -2 s -1 AugStable running period to consolidate operation and MP ~2 MJ per beam 4-10 SeptCommissioning of 10A/s ramp, transverse FB, Xing angle studies No physics ! 10-22 SeptCommissioning of bunch trains, setting up of protection devices No physics ! 23Sept-14 OctStable beams with increasing k b (56  104  152  200  248  ….) ~15 MJ per beam, L ~ 10 32 cm -2 s -1

16. fill 1418, ~ 10 11, k b =248 Peak Luminosity 10 32 cm -2 s -1 Integrated luminosity over the fill > 2.4 (pb)^-1

17. Integrated Luminosity delivered So far

18. Status of the machine in short Overall good availability (special mention for Cryogenics) Key systems performing well, still some cleanup Injection Beam dumping Collimation Beam interlocking system ( Machine Protection ) RF (power, longitudinal blow up and transverse feedback … Magnetically well understood and reproducible Feedbacks on orbit and tunes operational through all cycle Aperture is even better than expected Small emittances, nominal bunch intensities Excellent single beam lifetimes (vacuum, RF, optics) Beam-beam is there but well under control (transverse FB, crossing angles)

19. Optics stability

20. 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

21. 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/s10 A/s 450 GeV 3500 GeV

22. 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

23. Q’ during injection, ramp and flat top

24. Feedbacks on orbit and tunes

25. Evidence of Beam-beam Coherent beam-beam instabilities observed in July Stabilized first with Octupoles and then with transverse FB

26. Transverse feedback Injection oscillations, dampers off Injection oscillations, dampers on

27. Lifetime when Reducing Crossing Angle 3 batches of 8 bunches each, spacing 150 ns  up to 6 parasitic interactions per bunch 100  rad 170  100  rad 80  rad 70  rad 60  rad 50  rad 40  rad 30  rad 20  rad 90  rad  Minimum required X-ing angle is ~100  rad in 2010

28. 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 sigma Orbit and mechanical tolerances much better than anticipated

29. Some issues increasing total intensity Tune measurement at high beam currents  solved Before After change of FE

30. 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

31. FAST losses bypassing the collimation (UFO) Arc and DS BLM threshold increased by a factor 3. Seems to work with 248 bunches

32. Schedule – rest of 2010 32

33. Early Heavy Ion Run Parameters 33 Early (2010/11) (3.5 Z TeV) Nominal (7 TeV) √ s per nucleon TeV1.385.5 Initial Luminosity (L 0 ) cm -2 s -1 ~10 25 10 27 Number of bunches 62592 Bunch spacing ns135099.8 ** m3.50.5 Pb ions/bunch 7x10 7 Transverse norm. emittance mm 1.5 Luminosity half life (1,2,3 expts.) h  IBS =7-30 8, 4.5, 3 Initial interaction rate: 100 Hz, ~10 8 interaction/10 6 s (~1 month)

34. Possible performance improvements in 2011 being (carefully) considered Run at higher N/ε? Interesting beam physics: where is the real limit? Increase bunch intensity Decrease transverse emittance further Machine protection implications to be assessed Run at higher energy…waking up the dragon? Risk assessment to be redone after experience with beam in 2010 No beam induced quenches so far, better knowledge of quench limits (from tests with beam) RRR measurements Quench propagation measurements

35. 2011 Q1&2 35

36. 2011 Q3&4 36

37. The 10 year technical Plan