1. 24.08.2010 LHC Status - SUSY 2010 - Bonn 1 Drawing by Sergio Cittolin Status of the LHC 6 months of beam operation in 2010 J. Wenninger CERN

2. Outline 24.08.2010 LHC Status - SUSY 2010 - Bonn 2 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conclusions

3. 24.08.2010 LHC Status - SUSY 2010 - Bonn The Large Hadron Collider LHC 3 CMS, Totem ATLAS, LHCf LHCbLHCb ALICEALICE Lake of Geneva Installed in 26.7 km LEP tunnel Depth of 70-140 m Control Room LHC ring SPS ring

4. LHC layout and parameters 4  8 arcs (sectors), ~3 km each  8 long straight sections (700 m each)  beams cross in 4 points  2-in-1 magnet design with separate vacuum chambers → p-p collisions - - β * = 0.55 m (beam size =17 μm) - Crossing angle = 285 μrad - L = 10 34 cm -2 s -1 RF Nominal LHC parameters Beam energy (TeV)7.0 No. of particles per bunch1.15x10 11 No. of bunches per beam2808 Stored beam energy (MJ)362 Transverse emittance (μm)3.75 Bunch length (cm)7.55

5. LHC accelerator complex 5 Beam 1 TI2 Beam 2 TI8 LHC proton path The LHC needs most of the CERN accelerators... ≥ 7 seconds from source to LHC

6. LHC challenges 24.08.2010 LHC Status - SUSY 2010 - Bonn 6 The LHC surpasses existing accelerators/colliders in 2 aspects :  The energy of the beam of 7 TeV that is achieved within the size constraints of the existing 26.7 km LEP tunnel. LHC dipole field8.3 T HERA/Tevatron ~ 4 T  The luminosity of the collider that will reach unprecedented values for a hadron machine: LHC pp ~ 10 34 cm -2 s -1 Tevatron pp3x10 32 cm -2 s -1 SppSpp6x10 30 cm -2 s -1 Very high field magnets and very high beam intensities:  Operating the LHC is a great challenge.  There is a significant risk to the equipment and experiments. A factor 2 in field A factor 4 in size A factor 30 in luminosity

7. LHC dipole magnet 24.08.2010 LHC Status - SUSY 2010 - Bonn 7  1232 dipole magnets.  B field 8.3 T (11.8 kA) @ 1.9 K (super-fluid Helium)  2 magnets-in-one design : two beam tubes with an opening of 56 mm.  Operating challenges: o Dynamic field changes at injection. o Very low quench levels (~ mJ/cm 3 )

8. Stored energy 24.08.2010 LHC Status - SUSY 2010 - Bonn 8 Increase with respect to existing accelerators : A factor 2 in magnetic field A factor 7 in beam energy A factor 200 in stored beam energy Damage threshold

9. Collimation 24.08.2010 LHC Status - SUSY 2010 - Bonn 9 beam 1.2 m  To operate at nominal performance the LHC requires a large and complex collimation system o Previous colliders used collimators mostly for experimental background conditions.  Ensure ‘cohabitation’ of: o 360 MJ of stored beam energy, o super-conducting magnets with quench limits of few mJ/cm 3  Almost 100 collimators and absorbers.  Alignment tolerances < 0.1 mm to ensure that over 99.99% of the protons are intercepted.  Primary and secondary collimators are made of Carbon to survive large beam loss.

10. Outline 24.08.2010 LHC Status - SUSY 2010 - Bonn 10 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conclusions

11. LHC target energy: the way down 24.08.2010 LHC Status - SUSY 2010 - Bonn 11 2002-2007 7 TeV Summer 20085 TeV Spring 2009 3.5 TeV Nov. 2009 450 GeV Detraining nQPS 2 kA 6 kA 9 kA WhenWhy 12 kA Late 2008 Joints 1.18 TeV Design  All main magnets commissioned for 7TeV operation before installation  Detraining found when hardware commissioning sectors in 2008 –5 TeV poses no problem –Difficult to exceed 6 TeV  Machine wide investigations following S34 incident showed problem with joints  Commissioning of new Quench Protection System (nQPS)

12. LHC target energy: the way up 24.08.2010 LHC Status - SUSY 2010 - Bonn 12  Train magnets –6.5 TeV is in reach –7 TeV will take time  Repair joints  Complete pressure relief system  Commission nQPS system 2014 ? 2010 Training Stabilizers nQPS WhenWhat 7 TeV 3.5 TeV 1.18 TeV 450 GeV 2011 2013 2009 6 TeV

13. Ramp rate 24.08.2010 LHC Status - SUSY 2010 - Bonn 13  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) were increased to nominal value of 10 A/s (6 GeV/s).  Ramp speed with beam will be increased to 10 A/s (6 GeV/s) in September. o Ramp duration 0.45-3.5 TeV: 16 minutes 2 A/s10 A/s 450 GeV 3500 GeV

14. Outline 24.08.2010 LHC Status - SUSY 2010 - Bonn 14 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2011 and conclusions

15. Collider luminosity 24.08.2010 LHC Status - SUSY 2010 - Bonn 15 “Thus, to achieve high luminosity, all one has to do is make (lots of) high population bunches of low emittance to collide at high frequency at locations where the beam optics provides as low values of the amplitude functions as possible.” PDG 2005, chapter 25  Parameters: –Number of particles per bunch  –Number of bunches per beamk b –Beam sizes at the collision point  –Betatron function (focusing) at IP  * –Normalized transverse emittance  –Revolution frequencyf –Crossing angle factor F ~ 1 Collision rate is proportional to luminosity Interaction Region Beam quality (emittance) Intensity

16. Collimation performance 24.08.2010 LHC Status - SUSY 2010 - Bonn 16  I max ~6  10 13 protons per beam at 3.5TeV with intermediate collimator settings  (about 20% nominal intensity) 30 MJ stored beam energy Present stage collimation system sets limit to total intensity.  Assumptions: o Max. loss rate of 0.1%/s assumed (0.2h lifetime). o Ideal cleaning.  Performance degradation: o Deformed jaws. o Tilt & offset & gap errors. o Machine alignment.  Machine stability o Tight coll. settings are a challenge at early stage. o Intermediate coll. settings make use of aperture to relax tolerances. Collimator settings

17. Goals for 2010-2011 17 Repair of Sector 34 1.18 TeV nQPS 6kA 3.5 TeV I safe < I < 0.2 I nom β* ~ 3.5 m Ions 3.5 TeV ~ 0.2 I nom β* ~ 3.5 m Ions 200920102011 No BeamBBeam Goal for the 2010-11 run: Collect 1 fm -1 of data/exp at 3.5 TeV/beam. To achieve this goal the LHC must operate in 2011 with L ~ 2×10 32 cm -2 s -1 ~ Tevatron Luminosity which requires ~700 bunches of 10 11 p each ~ 7x10 13 p (stored energy of ~30 MJ – 10% of nominal) Implications: Strict and clean machine setup. Machine protection systems at near nominal performance.

18. Commissioning phases 24.08.2010 LHC Status - SUSY 2010 - Bonn 18  Phase 1: low intensity commissioning of the LHC. o Low intensity single bunches. No/very limited risk of damage. o Commissioning of the protection systems.  Phase 2: operation without crossing angle. o Bunches with large spacing (> 1 - 2.5  s). o Up to around k b =50 bunches. o Simplified operation in the interaction regions. o Machine protection system running in.  Phase 3: operation with crossing angle. o Bunches with close spacing (≤ 150 ns). o Aim for ~400 bunches in 2010. We are at end of phase 2

19. Commissioning steps in 2010 24.08.2010 LHC Status - SUSY 2010 - Bonn 19  Restart with beam.  Commissioning to 3.5 TeV. o Low intensity beams.  First collisions at 3.5 TeV.  Squeeze (  * reduction) commissioning. o  * = 2 m for collisions (injection 10 /11 m).  Increase number of bunches to 13 per beam. o Bunch population N = 3  10 10 p ~ 30% of nominal.  Switch to nominal bunch intensity. o Luminosity ~N 2 Gain ~ 10 o Back off in  * to 3.5 m. Loss ~ 0.6  Increase number of bunches up to 49 per beam. o Bunch population N = 9-10  10 10 p. o Stability run in August with 25 bunches/beam. Feb. 28th March March 30 th Mid April Mid-April – mid-May June July - August

20. Peak luminosity performance 24.08.2010 LHC Status - SUSY 2010 - Bonn 20 8 colliding pairs/IR 36 colliding pairs Peak luminosity = 9.5  10 30 cm -2 s -1 (48 bunches/beam, 36 colliding bunches)

21. Integrated luminosity 24.08.2010 LHC Status - SUSY 2010 - Bonn 21 Integrated luminosity ~ 2.2 pb -1 (23.08.2010) Figures : status 16 th Aug 2010

22. Availability 24.08.2010 LHC Status - SUSY 2010 - Bonn 22  About 30% of time in physics data-taking. o A lot commissioning still on-going ! o Min. turn-around time collisions to collisions ~4 hours. 3.5 TeV 6.5  10 30 cm -2 s -1 Energy Lumi 01 – 21 August 2010

23. Outline 24.08.2010 LHC Status - SUSY 2010 - Bonn 23 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conslusions

24. Machine Protection 24.08.2010 LHC Status - SUSY 2010 - Bonn 24  Extensive testing of the machine protection system was performed, mostly in March/April 2010. o  20’000 signal enter the beam abort system.  Only about 10% of the beams above injection energy are dumped by the operators ! Beam dumps > 450 GeV

25. Beam dump 24.08.2010 LHC Status - SUSY 2010 - Bonn 25 Extraction kickers Dilution kickers Extraction septum magnets Dump block  Complex beam dumping system commissioned. Beam swept over dump surface (power load)

26. Aperture and collimation 24.08.2010 LHC Status - SUSY 2010 - Bonn 26 Primary 6 σ Secondary 8.8 σ Dump Protection 10.5 σ Tertiary 15 σ Triplet 18 σ  With collisions the aperture limit of the LHC is in the strong focusing quadrupoles (triplets) that are installed just next to the experiments. o Hierarchy of collimators must be preserved in all phases to avoid quenching super-conducting magnets and for damage protection. o  * is presently limited to 3.5 m by aperture and tolerances. Collimation hierarchy Exp.

27. Collimation 24.08.2010 LHC Status - SUSY 2010 - Bonn 27  Collimator alignment is made with beam and then monitored from the loss distribution around ring.  Beam cleaning efficiencies ≥ 99.98% ~ as designed TCT = tertiary coll.

28. Magnet quenches 24.08.2010 LHC Status - SUSY 2010 - Bonn 28  A local loss of some ~10 7 protons/s may lead to a quench at 3.5 TeV. o Compared to 5  10 12 stored protons.  So far no quench was observed at 3.5 TeV thanks to the excellent performance of the collimation system for absorbing lost protons and to the fast reaction of the loss monitors.  In only 5 occasions did some beam escape and was lost locally around super-conducting elements. o Beam loss detection system dumped the beams in time before a magnet could quench. o Events are under investigation... Possible cause are dust particles! The absence of problems with beam loss and quenches is good news for increasing the beam intensity !

29. Beam Optics 24.08.2010 LHC Status - SUSY 2010 - Bonn 29  Beam optics is within specifications and reproducible over 3 months. o A stable machine is essential to reach high intensity and minimize frequent setup overhead, in particular for collimation. Relative beam size error   (  Specification:  0.2

30. Beam Emittance 24.08.2010 LHC Status - SUSY 2010 - Bonn 30 Momentum and magnetic fields at the LHC are sufficiently strong for the protons to emit visible light that can be used to image the beams in real-time. The energy loss per turn is 7 keV at 7 TeV, 0.4 keV at 3.5 TeV.  Beam emittances below nominal can be produced and injected into the LHC (  = 2  m rad as compared to 3.5  m rad design).  This provides margin for emittance blow-up due to various noise sources – great value for a machine in early phase of operation.  Beam emittances in collisions are now mostly at design or below – the only exception being beam 2 in the vertical plane.

31. Noise on the beam 24.08.2010 LHC Status - SUSY 2010 - Bonn 31  The beams are periodically excited by an unknown noise source (‘hump’) of varying frequency – affects mostly beam2 in vertical plane. o Amplitude ~  m.  When the frequency coincides with the beam eigen-modes (‘tunes’) it leads to emittance blow-up. Beam 1 Beam 2 Horizontal plane Vertical plane Frequency/Rev. frequency Time  1 hour Noise hump Tune

32. Beam-beam interaction 24.08.2010 LHC Status - SUSY 2010 - Bonn 32 - blackwitness bunches (zero collisions); - red bunches colliding in IP 1 5 and 2 (3 collisions); - blue bunches colliding in IP 1 5 and 8 (3 collisions); - green bunches colliding in IP 2 and 8 (2 collisions).  Effects of the beam-beam force are visible on the lifetime of the various bunches. o Also sensitive to tune working point. o This will become even more complicated with trains of bunches. Beams in collision Beam1 Beam2 Intensity loss (%)

33. Lifetimes 24.08.2010 LHC Status - SUSY 2010 - Bonn 33  Beam intensity lifetimes with colliding beams: o Dip to 2-5 hours in first minutes. o Progressive increase to ~100 hours.  Luminosity lifetimes: o Around 20-30 hours due to emittance growth. Beams in collision Lifetime (h) 100 200 300

34. Present LHC parameters 24.08.2010 LHC Status - SUSY 2010 - Bonn 34 ParameterPresentNominalLimited by N (p/bunch) 1  10 11 1.15  10 11 k b (no. bunches)482808Machine protection  (  m rad) 2.5-53.75  * (m) 3.50.55Aperture, tolerances L (cm -2 s -1 ) 6.5  10 30 10 34  Squeezing at the IP (  *) is limited by aperture and tolerances. o Beams are larger at 3.5 TeV ~ 1/ . o  x =  y = ~45-60  m - nominal value is 15  m at 7 TeV.  The number of bunches is limited by machine protection and by the fact that LHC is not yet operated with bunch trains. o Bunch separation is large (>1  s), no crossing angle at the IR.

35. Outline 24.08.2010 LHC Status - SUSY 2010 - Bonn 35 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conclusions

36. Fall 2010 24.08.2010 LHC Status - SUSY 2010 - Bonn 36 336192 240 288 6 12 12 24 24 24 24 48 48 96 144 Switch to bunch trains Switch to bunch trains  To reach the target of 10 32 cm -2 s -1 an intensity increase of factor 10 is required until end of October (start of Pb ion run). o But the most important is the slope of the increase!

37. Fall 2010-2011 24.08.2010 LHC Status - SUSY 2010 - Bonn 37  To reach the target of 10 32 cm -2 s -1, o the intensity must be increased very rapidly, o bunch train operation must be commissioned (1-2 weeks). >> Achievable integrated L is ~ 25-50 pb -1 in 2010.  The goal is quite ambitious given the time left before the Pb ion run, but the main point is not the exact final luminosity, but rather that no problems or show-stoppers are encountered on the way. o So far there are no limitations.  The prospects for a very good run in 2011, 1 fm -1 of data, will be very high with a problem-free intensity (luminosity) increase in 2010. o But the most important is the slope of the increase!

38. Summary and outlook 2011 24.08.2010 LHC Status - SUSY 2010 - Bonn 38  Main beam commissioning phase of the LHC ended in June when operation with ~ nominal bunch intensities was established.  The LHC is now operating for physics data taking, with some interleaved commissioning activities in view of higher intensity. Efficiency for physics data taking ~30% with peak luminosities of 9.5x10 30 cm -2 s -1  Machine protection and collimation systems perform well, and one can anticipate a luminosity increase towards few 10 31 to 10 32 cm -2 s -1 in 2010. Final value for 2010 will depend on machine availability and length of commissioning bunch train operation.  A long run at 10 32 cm -2 s -1 or above is in sight for 2011. 1 fm -1 of integrated data is in reach.