1. LHC: High Luminosity, UFOs and other surprises Even before the drawing-board stage, the farsighted John Adams noted in 1977 that the tunnel for a future large electron–positron (LEP) collider should also be big enough to accommodate another ring of magnets. Rüdiger Schmidt, CERN 23 July 2012 Hadron Collider Summer School Introduction to the LHC accelerator Accelerator physics and LHC performance limitations Machine protection, collimation and UFOs Beam operation in 2012 Acknowledgements for slides from T.Baer, M.Lamont, R.Steinhagen, D.Wollmann and J.Wenninger

2. LHC: A long story starting in the distant past l First ideas to first protons: from 1984 to 2008 l Tears of joy…. first beam in 2008 l Tears of sadness…first (and hopefully last) accident in 2008 l What doesn’t kill you makes you stronger l The story of the champagne bottles

3. l Introduction to LHC l Accelerator Physics Crash Course Why protons? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC layout and beam transport l High Luminosity and the consequences l High Energy and the consequences l Wrapping up: LHC Parameters l The CERN accelerator complex: injection and transfer l LHC superconducting magnets l Machine protection and collimation l LHC operation l Summary and conclusions Outline

4. Energy and Luminosity l Particle physics requires an accelerator colliding beams with a centre-of-mass energy substantially exceeding 1 TeV l In order to observe rare events, the luminosity should be in the order of 10 34 [cm -2 s -1 ] (challenge for the LHC accelerator) l Event rate: l Assuming a total cross section of about 100 mbarn for pp collisions, the event rate for this luminosity is in the order of 10 9 events/second (challenge for the LHC experiments) l Nuclear and particle physics require heavy ion collisions in the LHC (quark-gluon plasma.... )

5. LHC pp and ions 7 TeV/c 26.8 km Circumference CERN Main Site Switzerland Lake Geneva France LHC Accelerator (100 m down) SPS Accelerator CERN- Prevessin CMS, TOTEM ALICELHCbATLAS

6. The LHC: just another collider ? StartTypeMax proton energy [GeV] Length [m] B Field [Tesla] Lumi [cm -2 s -1 ] Stored beam energy [MJoule] TEVATRON Fermilab Illinois USA 1983p-pbar98063004.54.3 10 32 1.6 for protons HERA DESY Hamburg 1992p – e+ p – e- 92063005.55.1 10 31 2.7 for protons RHIC Brookhaven Long Island 2000Ion-Ion p-p 25038344.31.5 10 32 0.9 per proton beam LHC CERN 2008Ion-Ion p-p 7000 Now 4000 268008.310 34 Now 6 10 33 362 per Name beam Factor74250100

7. Accelerator Physics Crash Course

8. The hierarchy in physics DIE ZEIT 19/07/2012, citing Mike Lamont (Head of CERN accelerator operation): Und unter den Physikern gebe es eine Hierarchie: »Ganz oben stehen die Theoretiker, dann kommen die Experimentalphysiker und dann wir, die Maschinenleute.« Among physicists there is a hierarchy: » On top are the theorists, then the experimental physicist, then us, the machine people.« Accelerator physicist Experimental physicist Theorist

9. To accelerate a particle to high energy … l Particle energy about 10 kJoule

10. To get to 7 TeV: Synchrotron – circular accelerator and many passages in RF cavities LHC circular machine with energy gain per turn ~0.5 MeV acceleration from 450 GeV to 7 TeV will take about 20 minutes

11. Lorentz Force The force on a charged particle is proportional to the charge, the electric field, and the vector product of velocity and magnetic field: For an electron or proton the charge is: Acceleration (increase of energy) only by electrical fields – not by magnetic fields:

12. Particle deflection: superconducting magnets The force on a charged particle is proportional to the charge, the electric field, and the vector product of velocity and magnetic field given by Lorentz Force: z x s v B F Maximum momentum 7000 GeV/c Radius 2805 m fixed by LEP tunnel Magnetic field B = 8.33 Tesla Iron magnets limited to 2 Tesla, therefore superconducting magnets are required Deflecting magnetic fields for two beams in opposite directions

13. Deflection by 1232 superconducing dipole magnets Superconducting magnets in LHC tunnel

14. Particle acceleration: accelerating protons to 7 TeV Acceleration of the protons in an electrical field with 7 TV But:  no constant electrical field above some Million Volt (break down)  no time dependent electrical field above some 10 Million Volt (about 30 MV/m) 1 MeV requires U = 1 MV

15. LHC RF frequency 400 MHz Revolution frequency 11246 Hz Particle acceleration with RF cavity

16. RF systems: 400 MHz 400 MHz system: 16 sc cavities (copper sputtered with niobium) for 16 MV/beam were built and assembled in four modules

17. 400 MHz RF buckets and bunches EE time RF Voltage time LHC bunch spacing = 25 ns = 10 buckets  7.5 m 2.5 ns The particles are trapped in the RF voltage: this gives the bunch structure RMS bunch length 11.2 cm 7.6 cm RMS energy spread 0.031%0.011% 450 GeV 7 TeV The particles oscillate back and forth in time/energy RF bucket 2.5 ns

18. Limitation of the energy l LEP was operating with electrons and positrons with an energy of 103 GeV / particle l As a factory for Higgs (?), operation at 120 GeV would be required (....assuming that ATLAS and CMS results are confirmed) l This was just a little above the LEP limit l There is a large interest in exceeding the LEP energy by one order of magnitude (LHC => 7 TeV) l The LHC provides proton – proton collisions

19. Radius Lorenz Force = accelerating force Particle trajectory Radiation field charged particle Figure from K.Wille Energy loss for charged particles by synchrotron radiation

20. Energy loss for charged particles electrons / protons in LEP tunnel

21. LHC layout and beam transport

22. LHC Layout eight arcs (sectors) eight long straight section (about 700 m long) IR4: RF + Beam instrumentation IR5:CMS IR1: ATLAS IR8: LHC-B IR2: ALICE Injection Beams from SPS ??

23. Beam transport Need for getting protons on a circle: dipole magnets Need for focusing the beams: l Particles with different injection parameters (angle, position) separate with time Assuming an angle difference of 10 -6 rad, two particles would separate by 1 m after 10 6 m. At the LHC, with a length of 26860 m, this would be the case after 50 turns (5 ms !) l Particles would „drop“ due to gravitation l The beam size must be well controlled At the collision point the beam size must be tiny l Particles with (slightly) different energies should stay together

24. Magnets and beam stability l Dipole magnets To make a circle around LHC l Quadrupol magnets To keep beam particles together Particle trajectory stable for particles with nominal momentum l Sextupole magnets To correct the trajectories for off momentum particles Particle trajectories stable for small amplitudes (about 10 mm) l Multipole-corrector magnets Sextupole - and decapole corrector magnets at end of dipoles l Particle trajectories can become instable after many turns (even after, say, 10 6 turns)

25. Focusing using lenses as for light beams f1f1 x x Quadrupolemagnet – B-field zero in centre, linear increase (as an optical lense) Dipolemagnet – B-field in aperture constant z z

26. Assuming proton runs along s (=y), perpendicular to x and z z x x z s z s x Side view focusing Looking along proton trajectory Top view defocusing From Maxwell equations:

27. Focusing of a system of two lenses for both planes d = 50 m horizontal plane vertical plane To focuse the beams in both planes, a succession of focusing and defocusing quadrupole magnets is required: FODO structure

28. R.Schmidt A (F0D0) cell in the LHC arcs SSS quadrupole MQF sextupole corrector (MCS) decapole octupole corrector (MCDO) lattice sextupole (MS) lattice sextupole (MS) lattice sextupole (MS) orbit corrector special corrector (MQS) special corrector (MO) quadrupole MQD quadrupole MQF main dipole MB orbit corrector main dipole MB main dipole MB main dipole MB main dipole MB main dipole MB LHC Cell - Length about 110 m (schematic layout) Vertical / Horizontal plane (QF / QD) Quadrupole magnets controlling the beam size „to keep protons together“ (similar to optical lenses) 10000 magnets powered in 1700 electrical circuits

29. Particle stability and superconducting magnets - Quadrupolar- and multipolar fields Particle oscillations in quadrupole field (small amplitude) Harmonic oscillation after coordinate transformation Circular movement in phase space Particle oscillation assuming non-linear fields, large amplitude Amplitude grows until particle is lost (touches aperture) No circular movement in phasespace

30. Relevant parameters to remember l Betatron tune: number of oscillations of a proton within one turn l Closed orbit: deviation of the centre of the bunch from the ideal path (approximately a circle) l Resonances: if the value of the betatron tune is equal to, say, n+0.5 or n+0.3333, the beam is lost

31. Betatron tune measurement

32. LHC superconducting magnets

33. 1232 Dipole magnets Length about 15 m Magnetic Field 8.3 T Two beam tubes with an opening of 56 mm plus many other magnets, to ensure beam stability (1700 main magnets and about 8000 corrector magnets ) Dipole magnets for the LHC

34. Coils for Dipolmagnets

35. The superconducting state only occurs in a limited domain of temperature, magnetic field and transport current density Superconducting magnets produce high field with high current density Lowering the temperature enables better usage of the superconductor, by broadening its working range T [K] B [T] J [kA/mm 2 ] Operating temperature of superconductors (NbTi) J [kA/mm 2 ]

36. Beam tubes Supraconducting coil Nonmagetic collars Ferromagnetic iron Steelcylinder for Helium Insulationvacuum Supports Vacuumtank Dipole magnet cross section 16 mBar cooling tube Quadrupolemagnet

37. Operational margin of a superconducting magnet Bc Tc 9 K Applied Magnetic Field [T] Bc critical field 1.9 K quench with fast loss of ~5 · 10 9 protons quench with fast loss of ~5 · 10 6 protons 8.3 T 0.54 T QUENCH Tc critical temperature Temperature [K]

38. Movies dipole magnets

39. High Luminosity: many protons in the collider

40. High luminosity by colliding trains of bunches Number of „New Particles“ per unit of time: The objective for the LHC as proton – proton collider is a luminosity of about 10 34 [cm -2 s -1 ] LEP (e+e-) : 3-4 10 31 [cm -2 s -1 ] Tevatron (p-pbar) : some 10 32 [cm -2 s -1 ] B-Factories: > 10 34 [cm -2 s -1 ]

41. Luminosity parameters

42. Beam beam interaction determines parameters Beam size 16  m, for  = 0.5 m (  is a function of the lattice) Beam size given by injectors and by space in vacuum chamber Beam size 16  m, for  = 0.5 m (  is a function of the lattice) f = 11246 Hz with 2808 bunches (every 25 ns one bunch) L = 10 34 [cm -2 s -1 ]

43. …smallest beam size at experiments Quadrupole Collision point in experiment l Large beam size in adjacent quadrupole magnets l Separation between beams needed, about 10  l Limitation with aperture in quadrupoles l Limitation of β function at IP to 1 m (2011) and 0.6 m (2012)

44. u The 2 LHC beams are brought together to collide in a ‘common’ region u Over ~260 m the beams circulate in one vacuum chamber with ‘parasitic’ encounters (when the spacing between bunches is small enough)  Total crossing angle of about 300  rad Experimental long straight sections

45. 194 mm ATLAS IP ~ 260 m Common vacuum chamber Horizontal plane: the beams are combined and then separated Vertical plane: the beams are deflected to produce a crossing angle at the IP to avoid undesired encounters in the region of the common vacuum chamber  (  rad) ATLAS-145 / ver. ALICE 90 / ver. CMS 120 / hor LHCb-220 /hor ~ 7 mm Not to scale !  Separation and crossing: example of ATLAS

46. LHC Main Parameters

47. LHC Parameter Nominal20112012 Proton energy[TeV]7.03.54.0 Current in main dipoles[kA]11.856.06.8 Stored energy, dipole circuit (154 dipoles) [GJ]1.07~0.28~0.35 Protons per bunch-1.15 x 10 11 ~1.5 x 10 11 Number of bunches-28081380 Bunch spacing[ns]2550 Normalized emittance[mm]3.752.0 - 3.0 β* in IP1 and IP5[m]0.551.5 / 1.00.6 Stored energy / beam[MJ]362~116~130 Peak luminosity for ATLAS and CMS [cm -2 s -1 ]1.0 x 10 34 0.36 x 10 34 ~0.6 x 10 34 Integrated luminosity for ATLAS and CMS [fb -1 ]-5.615

48. LHC Parameter (energy) Nominal20112012 (intended) Proton energy[TeV]7.03.54.0 Current in main dipoles[kA]11.856.06.8 Stored energy, dipole circuit (154 dipoles) [GJ]1.07~0.28~0.35 Protons per bunch-1.15 x 10 11 ~1.5 x 10 11 Number of bunches-28081380 Bunch spacing[ns]2550 Normalized emittance[mm]3.752.0 - 3.0 β* in IP1 and IP5[m]0.551.5 / 1.00.6 Stored energy / beam[MJ]362~116~130 Peak luminosity for ATLAS and CMS [cm -2 s -1 ]1.0 x 10 34 0.36 x 10 34 ~0.6 x 10 34 Integrated luminosity for ATLAS and CMS [fb -1 ]-5.615

49. LHC Parameter (luminosity) Nominal20112012 Proton energy[TeV]7.03.54.0 Current in main dipoles[kA]11.856.06.8 Stored energy, dipole circuit (154 dipoles) [GJ]1.07~0.28~0.35 Protons per bunch-1.15 x 10 11 ~1.5 x 10 11 Number of bunches-28081380 Bunch spacing[ns]2550 Normalized emittance[mm]3.752.0 - 3.0 β* in IP1 and IP5[m]0.551.5 / 1.00.6 Stored energy / beam[MJ]362~116~130 Peak luminosity for ATLAS and CMS [cm -2 s -1 ]1.0 x 10 34 0.36 x 10 34 ~0.6 x 10 34 Integrated luminosity for ATLAS and CMS [fb -1 ]-5.615

50. Very high beam luminosity: consequences l High energy stored in the beams l Dumping the beam in a safe way l Avoiding beam losses, in particular in the superconducting magnets Beam induced magnet quenching (when 10 -8 -10 -7 of beam hits magnet at 7 TeV) Beam cleaning (Betatron and momentum cleaning) l Radiation, in particular in experimental areas from beam collisions (beam lifetime is dominated by this effect) Single event upset in the tunnel electronics l Beam instabilities due to impedance and beam–beam effects l Photo electrons, generated by beam losses - accelerated by the following bunches – lead to instabilities

51. LHC Layout eight arcs (sectors) eight long straight section (about 700 m long) IR4: RF + Beam instrumentation IR5:CMS IR1: ATLAS IR8: LHC-B IR2: ALICE Injection IR6: Beam dumping system IR3: Moment Beam Cleaning (warm) IR7: Betatron Beam Cleaning (warm) Beam dump blocks Detection of beam losses with >3600 monitors around LHC Signal to kicker magnet Beams from SPS

52. Machine Protection and Collimation

53. HASCO 2012 Rüdiger Schmidt Energy stored magnets and beam

54. What does this mean? 360 MJoule: the energy stored in one LHC beam corresponds approximately to… 90 kg of TNT 8 litres of gasoline 15 kg of chocolate It’s how ease the energy is released that matters most !! The energy of an 200 m long fast train at 155 km/hour corresponds to the energy of 360 MJoule stored in one LHC beam

55. 55 Controlled SPS experiment l 8  10 12 protons clear damage l beam size σ x/y = 1.1mm/0.6mm above damage limit for copper stainless steel no damage l 2  10 12 protons below damage limit for copper 6 cm 25 cm Damage limit ~200 kJoule 0.1 % of the full LHC 7 TeV beams factor of ~10 below the energy in a bunch train injected into LHC V.Kain et al A B D C SPS experiment: Beam damage with 450 GeV proton beam

56. 56 Beam losses In accelerators, particles are lost due to a variety of reasons End of a physics fill Beam-gas interaction Losses from collisions Losses due to the beam halo touching the aperture Losses due to instabilities l Continuous beam losses are inherent to the operation of accelerators Taken into account during the design of the accelerator l Accidental beam losses are due to a multitude of failures mechanisms l The number of possible failures leading to accidental beam loss is (nearly) infinite

57. Layout of beam dump system in IR6 Beam 2 Beam dump block Kicker magnets to paint (dilute) the beam about 700 m about 500 m 15 fast ‘kicker’ magnets deflect the beam to the outside When it is time to get rid of the beams (also in case of emergency!), the beams are ‘kicked’ out of the ring by a system of kicker magnetsd send into a dump block ! Septum magnets deflect the extracted beam vertically quadrupoles The 3  s gap in the beam gives the kicker time to reach full field. Ultra-high reliability system !!

58. Dump line in IR6

59. Dump line

60. Dump installation CERN visit McEwen 60

61. Beam dump with 1380 bunches Beam spot at the end of the beam dumping line, just in front of the beam dump block

62. 62 Beam losses, machine protection and collimation Continuous beam losses Collimation prevents too high beam losses around the accelerator (beam cleaning) A collimation system is a (very complex) system installed in the LHC to capture mostly halo particles Such system is also called (beam) Cleaning System Accidental beam losses “Machine Protection” protects equipment from damage, activation and downtime Machine protection includes a large variety of systems

63. RF contacts for guiding image currents Beam spot 2 mm View of a two sided collimator about 100 collimators are installed in LHC Ralph Assmann, CERN length about 120 cm

64. Betatron beam cleaning Cold aperture Cleaning insertion Arc(s)IP Circulating beam Illustration drawing Arc(s) Primary collimator Secondary collimators Tertiary beam halo + hadronic showers Shower absorbers Tertiary collimators SC Triplet

65. Ionization chambers to detect beam losses: Reaction time ~ ½ turn (40  s) Very large dynamic range (> 10 6 ) There are ~3600 chambers distributed over the ring to detect abnormal beam losses and if necessary trigger a beam abort ! Beam Loss Monitors

66. Rüdiger Schmidt Continuous beam losses during collisions 66 CMS Experiment ATLAS Experiment LHC Experiment ALICE Experiment Momentum Cleaning RF and BI Beam dump Betatron Cleaning

67. Measurement: 500kJ losses at primary collimators (loss rate: 9.1e11 p/s) – IR7 Daniel Wollmann TCP: ~505 kJ Q8L7: ~335 J Q11L7: ~35 J Q19L7: ~4.7 J Q8L7:  ~ 6.7e-4 Lower limit: R q L dil ~ 1.22e9 p/s (with c resp = 2 ) Lost energy over 1 s

68. Strategy for protection and related systems l Avoid that a specific failure can happen l Detect failure at hardware level and stop beam operation l Detect initial consequences of failure with beam instrumentation ….before it is too late… l Stop beam operation stop injection extract beam into beam dump block stop beam by beam absorber / collimator l Elements in the protection systems hardware monitoring and beam monitoring beam dump (fast kicker magnet and absorber block) collimators and beam absorbers beam interlock systems linking different systems

69. Machine Protection at Injection …throwing 3 MJ at LHC

70. HASCO 2012 Rüdiger Schmidt SPS, transfer line and LHC 1 km Beam is accelerated in SPS to 450 GeV (stored energy of 3 MJ) Beam is transferred from SPS to LHC Beam is accelerated in LHC to 3.5 TeV (stored energy of 100 MJ) Scraping of beam in SPS before transfer to LHC Transfer line 3km LHC SPS 6911 m 450 GeV / 400 GeV 3 MJ Acceleration cycle of ~10 s CNGS Target IR8 Switching magnet Fast extraction kicker Injection kicker Transfer line Injection kicker IR2 Fast extraction kicker

71. HASCO 2012 Rüdiger Schmidt Protection at injection LHC circulating beam Circulating beam in LHC LHC vacuum chamber Transfer line vacuum chamber

72. HASCO 2012 Rüdiger Schmidt LHC circulating beam Beam injected from SPS and transfer line Protection at injection Beam from SPS Injection Kicker LHC injected beam

73. HASCO 2012 Rüdiger Schmidt LHC circulating beam Kicker failure (no kick) Protection at injection Beam from SPS Injection Kicker

74. HASCO 2012 Rüdiger Schmidt LHC circulating beam Beam absorbers take beam in case of kicker misfiring Transfer line collimators ensure that incoming beam trajectory is ok Protection at injection Beam from SPS Injection Kicker Set of transfer line collimators (TCDI) ~5σ Injection absorber (TDI) ~7σ phase advance 90 0

75. HASCO 2012 Rüdiger Schmidt LHC circulating beam Beam absorbers take beam in case of kicker misfiring on circulating beam Protection at injection Injection Kicker Injection absorber (TDI) ~7σ Circulating beam – kicked out phase advance 90 0 LHC circulating beam Set of transfer line collimators (TCDI) ~5σ

76. Understanding LHC operation Filling Ramp Squeeze Adjust Stable beams Pilot beam Batches Closed orbit Beta function Betatron tunes Emittance Impedance

77. From first year to first fb-1 2008 First beam in LHC 2010 First fb-1

78. From 2010….

79. …..to 2012 1 fb-16 fb-1

80. Excellent fill 2195 in 2011 A nice long fill of about 18 hours…… Injection and ramp Stable beams Beam dump

81. Beam Intensities and Luminosity, 11-18/6/2012 Stable performance Mixed bag Stable performance

82. Overview of fills LHC 8:30 meeting FillDurationIbeamLpeak [e30 cm-2s-1] Lint [pb-1] Dump 27232:262.03E+14640646.06Trip of ROD.A81B1, SEU? 27241:132.03E+14632925.905Electrical perturbation 27257:042.05E+146520115.5Trip of S81 27268:582.05E+146499142.5 Elecitrical perturbation, FMCM 272811:412.06E+146525171.5Operator dump 27293:282.06E+14650267.7BLM self trigger 27321:522.06E+146592.540QPS trigger RQX.R1, SEU? 273312:342.06E+146674183Triplet RQX.L2 tripped. 273415:332.01E+146257.5203.5Operator dump 273617:292.02E+146465.5233Operator dump 27373:361.99E+14602166.1RF Trip 2B2 Total51.1%1301 51 % of time in stable beams; total of 1.3 fb-1 in one week !

83. Good fill 2195 in 2011 – start of the fill Start injection End injection Start energy ramp End energy ramp 3.5 TeV ~1 hour

84. Reference fill 2195 in 2011 – at 3.5 TeV Start ramp to collisiong Squeezing Energy ramp to 3.5 TeV Bringing beams into collision

85. Luminosity increase

88. l To increase the luminosity, the beta function was reduced between 2011 and 2012 from 1.0 m to 0.6 m l This reduces the beam size in the experiments, and increases the beam size in the adjacent quadrupole magnets (inner triplets)

89. …beam size at experiments in 2011 Collision point in experiment l Crossing angle to avoid parasitic beam-beam interaction l Minimum separation in the order of 10  (  rms beam size) Quadrupole

90. …becoming smaller during more squeezing Collision point in experiment l β function at IP down to 0.6 m in 2012 l Larger beam size in quadrupole magnets l Higher energy: emittance decreases for protons l Separation needs to increase to keep 10  l Problems with aperture in quadrupoles l Collimators need to be set tighter Quadrupole

91. Record fill 2692 in 2012, max. integrated luminosity Start energy ramp End energy ramp 4 TeV

92. Fill 2701, typical fill in 2012 R.Schmidt 92 end squeeze and start adjust end adjust start squeeze

93. Fill 2602, also a typical fill in 2012……. R.Schmidt 93 21:41:24 start squeeze 21:57:33 start adjust 22:07:15 end adjust 21:37:59 end ramp

94. Rüdiger Schmidt BLM system: beam losses before collisions CMS Experiment ATLAS Experiment LHC Experiment ALICE Experiment Momentum Cleaning RF and BI Beam dump Betatron Cleaning

95. Rüdiger Schmidt Continuous beam losses during collisions 95 CMS Experiment ATLAS Experiment LHC Experiment ALICE Experiment Momentum Cleaning RF and BI Beam dump Betatron Cleaning

96. Rüdiger Schmidt 2.An object falls into the beam

97. Rüdiger Schmidt Continuous beam losses during collisions 97 CMS Experiment ATLAS Experiment LHC Experiment ALICE Experiment Momentum Cleaning RF and BI Beam dump Betatron Cleaning

98. Rüdiger Schmidt Accidental beam losses during collisions 98 CMS Experiment ATLAS Experiment LHC Experiment ALICE Experiment Momentum Cleaning RF and BI Beam dump Betatron Cleaning

99. Rüdiger Schmidt Zoom one monitor: beam loss as a function of time 1 ms

100. Rüdiger Schmidt UFOs at LHC

101. Rüdiger Schmidt

126. 2012 Achieved vs. Target Luminosity Estimates from Moriand (Mike Lamont & Steve Myers) Assumptions – 4 TeV, 50 ns, 1380 bunches, 1.6e11, 2.5 um, pile-up ~ 35 – 150 days of proton physics (assuming similar efficiencies to 2011) Initial slow recovery a technical stop, but eventually caught up Presently operating with ~1 fb -1 /week

127. What we learned….. l Head-on beam-beam effect is not a limitation l Long range beam-beam effect has to be taken seriously Need separation of 10 -12 σ (otherwise bad lifetime and beam loss) l Small as possible emittances are good l Established β* reach (aperture, collimation, optics) l Luminosity levelling via offset tested – works fine in LHCb! l High-intensity operation close to beam instability limits l Instabilities were observed and are not fully understood for small IP beam offsets while going into collisions, …. impedances (kicker, collimator heating), collective effects,... l Availability Single Event Upsets, vacuum pressure increase, UFOs, cryogenics, magnet protection system,..…) – vigorous follow-up and consolidation

128. LHC Operation after the shutdown 2013/14 l Energy 6.5 TeV during 2015 l Bunch spacing 25 ns (in case of problem fall back to 50 ns) l Beta-function at experiments ~0.5 m l Pile-up of events in the experiments– assume acceptable Depends on bunch spacing and squeeze beyond 0.5 m Beta* luminosity-levelling to mitigate the initial large pile-up l Performance could be impacted by UFOs at higher energy and with 25 ns buch spacing Radiation to electronics – SEU’s Electron cloud & high energy & at 25 ns Long-range beam-beam & smaller crossing angle & at 25 ns Single- and bunch-by-bunch beam instabilities (impedances...) l It should be possible to achieve nominal luminosity of 10 34 [cm -2 s -1 ] or more

129. Summary In 2012 the peak luminosity exceeded 6x10 33 cm -2 s -1 in ATLAS and CMS with beams of 50 ns spacing The stored energy of the beams exceeded by a factor ~50 that of existing or previous machines No beam induced magnet quench was observed with stored beams Operation in 2012 is at 4.0 TeV Integrated luminosity for 2012 is in excess of 7 fm -1, hope to reach 15-20 fm -1 until the end of the run in February 2013 The consolidation of the splices between magnet will be done in 2013/14 to restart in 2015 at about 6.5 TeV UFOs could become a limitation for the availability of LHC at 6.5 TeV

130. Thanks for your attention

131. Reserve slides

132. LHC nominal energy is 7 TeV Why 3.5 TeV in 2011 and 4 TeV in 2012 ?

133. Accident in 2008 l Commissioning of main dipole circuit in last LHC sector: ramp to 9.3 kA (5.5 TeV) l At 8.7 kA an electrical fault developed in a dipole bus bar interconnection between a quadrupole and dipole l Later correlated to a local resistance of ~220 nOhm – nominal value 0.35 nOhm l An electrical arc developed which punctured the helium enclosure and the beam vacuum tube l Secondary arcs developed along the sector l Around 400 MJ from a total of 600 MJ were dissipated in the cold-mass and in electrical arcs l Large amounts of helium were released into the insulating vacuum, in total 6 tons were released

134. Rupture of high current cable between two magnets 12 kA cable

135. Pressure inside the cryostats Self actuating relief valves could not handle the pressure designed for 2 kg He/s, incident ~ 20 kg/s Large forces exerted on the vacuum barriers (every 2 cells, 230 m) designed for a pressure of 1.5 bar, incident ~ 10 bar Several quadrupoles displaced by up to ~50 cm Connections to the cryogenic line damaged in some places

136. Incident location Dipole bus bar

137. Quadrupole-dipole interconnection (27R3) Quadrupole support 39 dipoles out of 154 14 quadrupole short straight sections (SSS) out of 52 …had to be moved to the surface for control, repair or replacement Collateral damage : displacements

138. Incident in 2008, caused by a bad splice

139. 4 TeV - limitation of energy To reach nominal energy of 7 TeV requires a consolidation campaign of the connections (will take more than one year, requires full warm up of LHC) In order to avoid any risk, it was decided to limit the current in the main magnets and therefore the energy to 3.5 TeV for 2010 and 2011, and to 4.0 TeV for 2011 It turned out that there is still excellent physics at this energy, and it is planned to increase the energy to 6.5 TeV after the consolidation

140. Risk during a quench of a main dipole 1 quench/month If during 2012 the number of high current quenches stays below 5-6 then we have the same probability of burn-out as during 3.5 TeV run in 2011 with 40 quenches

141. Schematic of the main dipole circuit Global protection of the busbar and joints between magnets protection threshold 1 V (160 V inductive voltage during ramp) Local (quench) protection of each magnet

142. Long Shutdown LS1 l 2013 – 2014: LS1 consolidate LHC for 6.5 / 7TeV: l Measure all splices and repair the defective l Consolidate interconnects with new design (clamp, shunt) l Finish installation of pressure release valves (DN200) l Magnet consolidation l Electronics relocation, redesign, etc. to further reduce SINGLE EVENT EFFECTS on electronics l Install collimators with integrated button BPMs (tertiary collimators and a few secondary collimators) l Extensive parallel consolidation and upgrades of experiments

143. DN200 – He blow-hole LHC MB Circuit Splice Consolidation Plans Clamping and Shielding