1. J. Wenninger LNF Spring School, May 2010 1 LHC : construction and operation Part 2: Machine protection Incident and energy limits Commissioning and operation Jörg Wenninger CERN Beams Department / Operations group LNF Spring School 'Bruno Touschek' - May 2010

2. J. Wenninger LNF Spring School, May 2010 Machine protection 2

3. J. Wenninger LNF Spring School, May 2010 The price of high fields & high luminosity… 3 When the LHC is operated at 7 TeV with its design luminosity & intensity,  the LHC magnets store a huge amount of energy in their magnetic fields: per dipole magnet E stored = 7 MJ all magnets E stored = 10.4 GJ  the 2808 LHC bunches store a large amount of kinetic energy: E bunch = N x E = 1.15 x 10 11 x 7 TeV = 129 kJ E beam = k x E bunch = 2808 x E bunch = 362 MJ To ensure safe operation (i.e. without damage) we must be able to dispose of all that energy safely ! This is the role of machine protection !

4. J. Wenninger LNF Spring School, May 2010 Stored Energy 4 Increase with respect to existing accelerators : A factor 2 in magnetic field A factor 7 in beam energy A factor 200 in stored energy

5. J. Wenninger LNF Spring School, May 2010 Comparison… 5 The energy of an A380 at 700 km/hour corresponds to the energy stored in the LHC magnet system : Sufficient to heat up and melt 15 tons of Copper!! The energy stored in one LHC beam corresponds approximately to… 90 kg of TNT 10-12 litres of gasoline 15 kg of chocolate It’s how easily/quickly the energy is released that matters most !!

6. J. Wenninger LNF Spring School, May 2010 Machine protection: beam 6

7. J. Wenninger LNF Spring School, May 2010 To set the scale.. 7 Few cm long groove of an SPS vacuum chamber after the impact of ~1% of a nominal LHC beam (2 MJ) during an ‘incident’:  Vacuum chamber ripped open.  3 day repair. The same incident at the LHC implies a shutdown of > 3 months. >> Protection of the LHC must be much stricter and much more reliable !

8. J. Wenninger LNF Spring School, May 2010 Beam impact in a target 8 Courtesy N. Tahir / GSI 20 bunches180 bunches 100 bunches380 bunches The 7 TeV LHC beam can drill a hole through ~35 m of Copper Simulation of a 7 TeV LHC beam impact into a 5 m long Copper target

9. J. Wenninger LNF Spring School, May 2010 From a real 450 GeV beam… 9 A B D C ShotIntensity / p+ A1.2×10 12 B2.4×10 12 C4.8×10 12 D7.2×10 12 ~0.1% nominal LHC beam Cu plate ~20 cm inside the ‘target’. 30 cm 108 plates 6 cm Shoot a 450 GeV beam into a target…

10. J. Wenninger LNF Spring School, May 2010 ‘Safe’ beams at the LHC… 10 L ~ 2  10 28 cm -2 s -1 LHC 2010 ‘Safe beam’ ‘Un-safe beam’ 2011

11. J. Wenninger LNF Spring School, May 2010 Schematic layout of beam dump system in IR6 11 Q5R Q4R Q4L Q5L Beam 2 Beam 1 Beam dump block Kicker magnets to paint (dilute) the beam  700 m  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 magnets and send into a dump block ! Septum magnets deflect the extracted beam vertically quadrupoles The 3 ms gap in the beam gives the kicker time to reach full field. Ultra-high reliability system !!

12. J. Wenninger LNF Spring School, May 2010 The dump block 12 Approx. 8 m concrete shielding beam absorber (graphite)  The ONLY element in the LHC that can withstand the impact of the full beam !  The block is made of graphite (low Z material) to spread out the showers over a large volume.  It is actually necessary to paint the beam over the surface to keep the peak energy densities at a tolerable level ! Measurement Simulation

13. J. Wenninger LNF Spring School, May 2010 Dump line in IR6 13

14. J. Wenninger LNF Spring School, May 2010 Dump line 14

15. J. Wenninger LNF Spring School, May 2010 Dump installation 15

16. J. Wenninger LNF Spring School, May 2010 ‘Unscheduled’ beam loss due to failures 16 Beam loss over multiple turns (~millisecond to many seconds) due to many types of failures. Passive protection - Failure prevention (high reliability systems). -Intercept beam with collimators and absorber blocks. Active Protection - Failure detection (by beam and/or equipment monitoring) with fast reaction time (< 1 ms). - Fire beam dumping system. Beam loss over a single turn during injection, beam dump. In the event a failure or unacceptable beam lifetime, the beam must be dumped immediately and safely into the beam dump block Two main classes for failures (with more subtle sub-classes):  Because of the very high risk, the LHC machine protection system is of unprecedented complexity and size.  A general design philosophy was to ensure that there should always be at least 2 different systems to protect against a given failure type.

17. J. Wenninger LNF Spring School, May 2010 Failure detection example : beam loss monitors 17  Ionization chambers to detect beam losses: –N 2 gas filling at 100 mbar over-pressure, voltage 1.5 kV –Sensitive volume 1.5 l –Reaction time ~ ½ turn (40 ms) –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 !

18. J. Wenninger LNF Spring School, May 2010 Beam loss monitoring

19. J. Wenninger LNF Spring School, May 2010 Machine protection and quench prevention: collimation 19

20. J. Wenninger LNF Spring School, May 2010 Operational margin of SC magnet 20 Bc Tc 9 K Applied Field [T] Bc critical field 1.9 K quench with fast loss of ~few 10 9 protons quench with fast loss of ~10 6-7 protons 8.3 T / 7 TeV 0.54 T / 450 GeV QUENCH Tc critical temperature Temperature [K] The LHC is ~1000 times more critical than TEVATRON, HERA, RHIC

21. J. Wenninger LNF Spring School, May 2010 Quench levels 21 Example of the energy (mJ/cm 3 ) required to quench an LHC dipole magnet with an instantaneous loss.  Steep energy dependence.  Models are confirmed at 0.45 TeV.  The phase transition from the super-conducting to a normal conducting state is called a quench.  Quenches are initiated by an energy in the order of few milliJoules –Movement of the superconductor by several  m (friction and heat dissipation). –Beam losses. –Cooling failures. –..

22. J. Wenninger LNF Spring School, May 2010 Beam lifetime 22 Consider a beam with a lifetime  : Number of protons lost per second for different lifetimes (nominal intensity): t = 100 hours 10 9 p/s t = 25 hours 4x10 9 p/s t = 1 hour 10 11 p/s While ‘normal’ lifetimes will be in the range of 10-100 hours (in collisions most of the protons are actually lost in the experiments !!), one has to anticipate short periods of low lifetimes, down to a few minutes !  To survive periods of low lifetime we must intercept the protons that are lost with very high efficiency before they can quench a magnet : collimation! Quench level ~ 10 6-7 p

23. J. Wenninger LNF Spring School, May 2010 Collimation 23 A 4-stage halo cleaning (collimation) system is installed to protect the LHC magnets from beam induced quenches.  A cascade of more than 100 collimators is required to prevent the protons and their debris to reach the superconducting magnet coils.  The collimators will also play an essential role for protection by intercepting the beams.  the collimators must reduce the energy load into the magnets due to particle lost from the beam to a level that does not quench the magnets. in front of the exp. Exp. Detectors Courtesy C. Bracco

24. J. Wenninger LNF Spring School, May 2010 Collimator settings at 7 TeV 24 1 mm The collimator opening corresponds roughly to the size of Spain !  At the LHC collimators are essential for machine operation as soon as we have more than a few % of the nominal beam intensity at injection ! Opening ~3-5 mm Carbon jaw RF contact ‘fingers’

25. J. Wenninger LNF Spring School, May 2010 25 Collimation performance IR8 IR1 IR2 IR5 Momentum Cleaning Momentum Cleaning Dump Protection Measurements of the collimation efficiency from beam loss maps confirms the excellent performance : > 99.9% efficiency ! Collimation team Cleaning

26. J. Wenninger LNF Spring School, May 2010 Machine protection: magnets 26

27. J. Wenninger LNF Spring School, May 2010 27 Powering Sector LHC powering in sectors Sector 1 5 DC Power feed 3 DC Power 2 4 6 8 7 LHC 27 km Circumference  To limit the stored energy within one electrical circuit, the LHC is powered by sectors.  The main dipole circuits are split into 8 sectors to bring down the stored energy to ~1 GJ/sector.  Each main sector (~2.9 km) includes 154 dipole magnets (powered by a single power converter) and 47 quadrupoles.  This also facilitates the commissioning that can be done sector by sector !

28. J. Wenninger LNF Spring School, May 2010 Powering from room temperature source… 28 Water cooled 13 kA Copper cables ! Not superconducting ! 6 kA power converter

29. J. Wenninger LNF Spring School, May 2010 …to the cryostat 29 Feedboxes (‘DFB’) : transition from Copper cable to super-conductor Cooled Cu cables

30. J. Wenninger LNF Spring School, May 2010 Quench detection 30  When part of a magnet quenches, the conductor becomes resistive, which can lead to excessive local energy deposition (tT rise !!) due to Ohmic losses.  To protect the magnet: –The quench must be detected: this is done by monitoring the voltage that appears over the coil (R > 0). –The energy release is distributed over the entire magnet by force-quenching the coils using quench heaters (such that the entire magnet quenches !). –The magnet current is switched off within << 1 second. 18/04/10 Example of the voltage signals over 5 quenching dipole magnets (beam induced at injection). Threshold of quench protection system (QPS)

31. J. Wenninger LNF Spring School, May 2010 Quench - discharge of the energy 31 Magnet 1Magnet 2 Power Converter Magnet 154 Magnet i Protection of the magnet after a quench: The quench is detected by measuring the voltage increase over coil. The energy is distributed in the magnet by force-quenching using quench heaters. The current in the quenched magnet decays in < 200 ms. The current flows through the bypass diode (triggered by the voltage increase over the magnet). The current of all other magnets is dischared into the dump resistors. Discharge resistor

32. J. Wenninger LNF Spring School, May 2010 Dump resistors 32 Those large air-cooled resistors can absorb the 1 GJ stored in the dipole magnets (they heat up to few hundred degrees Celsius).

33. J. Wenninger LNF Spring School, May 2010 Machine protection philosophy 33 Power permit Power Converters QPS Cryo → Authorises power on → Cuts power off in case of fault → Authorises beam operation → Requests a beam dump in case of problems Collimators access RF Beam permit Experiments vacuum BLMs Warm Magnets Software interlocks Stored magnetic energy Stored beam energy Power PermitBeam Permit

34. J. Wenninger LNF Spring School, May 2010 Beam interlock system 34 Beam Interlock System Beam Dumping System Injection BIS PIC essential + auxiliary circuits WIC QPS (several 1000) Power Converters ~1500 AUG UPS Power Converters Magnets FMCM Cryo OK RF System Movable Devices Experiments BCM Beam Loss Experimental Magnets Collimation System Collimator Positions Environmental parameters Transverse Feedback Beam Aperture Kickers FBCM Lifetime BTV BTV screensMirrors Access System DoorsEIS Vacuum System Vacuum valves Access Safety Blocks RF Stoppers BLM BPM in IR6 Monitors aperture limits (some 100) Monitors in arcs (several 1000) Timing System (Post Mortem) CCC Operator Buttons Safe Mach. Param. Software Interlocks LHC Devices SEQ LHC Devices LHC Devices Timing Safe Beam Flag Over 20’000 signals enter the interlock system of the LHC that will send the beam into the dump block if any input signals a fault ! Isn’t it a miracle that it works !

35. J. Wenninger LNF Spring School, May 2010 Incident of September 19 th 2008 & Consequences 35

36. J. Wenninger LNF Spring School, May 2010 Event sequence on Sept. 19th 36 Introduction: on September 10 th when the first beam made it around the LHC, not all magnets had not been fully commissioned for 5 TeV. A few magnets were missing their last commissioning steps. The last steps were finished the week after Sept. 10 th.  Last commissioning step of the dipole circuit in sector 34 : ramp to 5.5 TeV.  At ~5.1 TeV an electrical fault developed in the dipole bus bar (the bus bar is the cable carrying the current that connects all magnet of a circuit). Later traced to an anomalous resistance of 200 n  (should be 0.3 n  ).  An electrical arc developed which punctured the helium enclosure. Secondary arcs developed along the arc. Around 400 MJ were dissipated in the cold-mass and in electrical arcs.  Large amounts of Helium were released into the insulating vacuum. In total 6 tons of He were released.

37. J. Wenninger LNF Spring School, May 2010 Pressure wave 37  Pressure wave propagates in both directions along the magnets inside the insulating vacuum enclosure.  Rapid pressure rise : –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). 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. –Beam vacuum to atmospheric pressure.

38. J. Wenninger LNF Spring School, May 2010 38 One of ~1700 bus-bar connections Dipole busbar

39. J. Wenninger LNF Spring School, May 2010 Incident location 39 Dipole bus bar

40. J. Wenninger LNF Spring School, May 2010 Collateral damage : displacements 40 Quadrupole-dipole interconnection Quadrupole support Main damage area ~ 700 metres.  39 out of 154 dipoles,  14 out of 47 quadrupole short straight sections (SSS) from the sector had to be moved to the surface for repair (16) or replacement (37).

41. J. Wenninger LNF Spring School, May 2010 Collateral damage : beam vacuum 41 Clean Copper surface. Contamination with multi- layer magnet insulation debris. Contamination with sooth.  60% of the chambers  20% of the chambers The beam vacuum was affected over entire 2.7 km length of the arc.

42. J. Wenninger LNF Spring School, May 2010 Quench - discharge of the energy 42 Magnet 1Magnet 2 Power Converter Magnet 154 Magnet i Discharge resistor  In case of a quench, the individual magnet is protected (quench protection and diode).  Resistances are switched into the circuit: the energy is dissipated in the resistances (current decay time constant of 100 s). >> the bus-bar must carry the current until the energy is extracted ! The bus-bar must carry the current for some minutes, through interconnections

43. J. Wenninger LNF Spring School, May 2010 Bus-bar joint 43  24’000 bus-bar joints in the LHC main circuits.  10’000 joints are at the interconnection between magnets. They are welded in the tunnel. Nominal joint resistance: 1.9 K 0.3 nΩ 300K ~10 μΩ For the LHC to operate safely at a certain energy, there is a limit to maximum value of the joint resistance.

44. J. Wenninger LNF Spring School, May 2010 Joint quality 44  The copper stabilizes the bus bar in the event of a cable quench (=bypass for the current while the energy is extracted from the circuit). Protection system in place in 2008 not sufficiently sensitive.  A copper bus bar with reduced continuity coupled to a superconducting cable badly soldered to the stabilizer can lead to a serious incident.  During repair work in the damaged sector, inspection of the joints revealed systematic voids caused by the welding procedure. X-ray of joint bus U-profile bus wedge SolderNo solder

45. J. Wenninger LNF Spring School, May 2010 superconducting cable with about 12 mm2 copper copper bus bar 280 mm2 Magnet  Everything is at 1.9 Kelvin.  Current passes through the superconducting cable. For 7 TeV : I = 11’800 A Normal interconnect, normal operation Interconnection joint (soldered) This illustration does not represent the real geometry current 45 Helium bath

46. J. Wenninger LNF Spring School, May 2010 copper bus bar 280 mm2 Magnet  Quench in adjacent magnet or in the bus-bar.  Temperature increase above ~ 9 K.  The superconductor becomes resistive.  During the energy discharge the current passes for few minutes through the copper bus-bar. superconducting cable interconnection Normal interconnect, quench 46

47. J. Wenninger LNF Spring School, May 2010 copper bus bar 280 mm2 Magnet  Interruption of copper stabiliser of the bus-bar.  Superconducting cable at 1.9 K  Current passes through superconductor. Non-conform interconnect, normal operation superconducting cable interconnection 47

48. J. Wenninger LNF Spring School, May 2010 copper bus bar 280 mm2 Magnet  Interruption of copper stabiliser.  Superconducting cable temperature increase to above ~9 K and cable becomes resistive.  Current cannot pass through copper and is forced to pass through superconductor during discharge. superconducting cable interconnection Non-conform interconnect, quench. 48

49. J. Wenninger LNF Spring School, May 2010 copper bus bar 280 mm2 Magnet  The superconducting cable heats up because of the combination of high current and resistive cable. superconducting cable interconnection Non-conform interconnect, quench. 49

50. J. Wenninger LNF Spring School, May 2010 copper bus bar 280 mm2 Magnet  Superconducting cable melts and breaks if the length of the superconductor not in contact with the bus bar exceeds a critical value and the current is high.  Circuit is interrupted and an electrical arc is formed. superconducting cable interconnection Non-conform interconnect, quench. Depending on ‘type’ of non-conformity, problems appear :  at different current levels.  under different conditions (magnet or bus bar quench etc). 50

51. J. Wenninger LNF Spring School, May 2010 copper bus bar 280 mm2 Magnet  Anomalous resistance at the joint heats up and finally quenches the joint – but quench remains very local.  Current sidesteps into Copper that eventually melts because the electrical contact is not good enough. September 19 th hypothesis superconducting cable quench at the interconnection 51 >> A new protection system will be installed this year to anticipate such incidents in the future: new Quench Protection System (‘nQPS’)

52. J. Wenninger LNF Spring School, May 2010 LHC repair and consolidation 52 14 quadrupole magnets replaced 39 dipole magnets replaced 204 electrical inter- connections repaired Over 4km of vacuum beam tube cleaned New longitudinal restraining system for 50 quadrupoles Almost 900 new helium pressure release ports 6500 new detectors and 250km cables for new Quench Protection System to protect busbar joints: nQPS Collateral damage mitigation

53. J. Wenninger LNF Spring School, May 2010 53 Mechanical clamping (not present in Tevatron and Hera …) A glimpse in the future: the consolidated connection  In the next long (> 1 year) shutdown all the connections will be re-done.  Latest design: o Better electrical contact o Mechanical clamping Courtesy F. Bertinelli

54. J. Wenninger LNF Spring School, May 2010 LHC energy target - way down 2002-2007 7 TeV Summer 2008 5 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 o 5 TeV poses no problem o Difficult to exceed 6 TeV Machine wide investigations following S34 incident showed problem with joints Commissioning of new Quench Protection System (nQPS) 54

55. J. Wenninger LNF Spring School, May 2010 LHC energy target - way up Train magnets o 6.5 TeV is within reach o 7 TeV will take time Repair joints Complete pressure relief system Commission nQPS system 2014 ? 2010 Training Joint repair nQPS WhenWhat 7 TeV 3.5 TeV 1.18 TeV 450 GeV 2011 2013 2009 6 TeV 55

56. J. Wenninger LNF Spring School, May 2010 Beam operation 56

57. J. Wenninger LNF Spring School, May 2010 Goals for 2010-2011 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 Ambitious goal for the 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 Hz/cm 2 ~ Tevatron Luminosity which requires ~700 bunches of 10 11 p/bunch (stored energy of ~ 30 MJ – 10% of nominal) Implications: Strict and clean machine setup. Machine protection systems at near nominal performance. β * inj β * min IP1 / IP5 11 m2 m IP2/IP8 10 m2 m IP5-TOTEM 11 m90 m Mininum β* in various IP’s 57

58. J. Wenninger LNF Spring School, May 2010 LHC schedule 58  Proton run until November.  Lead ion setup and run November and Decenber.

59. J. Wenninger LNF Spring School, May 2010 59 2010 commissioning milestones 27 th FebFirst injection 28 th FebBoth beams circulating 5 th MarchCanonical two beam operation 8 th MarchCollimation setup at 450 GeV 12 th MarchRamp to 1.18 TeV 15 th - 18 th MarchTechnical stop – dipoles magnets good for 3.5 TeV 19 th MarchRamp to 3.5 TeV 30 th MarchFirst 3.5 TeV collisions in all experiments (media event) 4 th - 5 th April 19h-long physics fill with  * 10/11 m - L ~ 10 27 cm -2 s -1 7 th April  *squeeze to 2 m in IP1 and IP5 24 th April 30h-long physics fill with  * of 2 m - L ~ 1.3  10 28 cm -2 s -1

60. J. Wenninger LNF Spring School, May 2010 LHC machine cycle 60 energy ramp preparation and access beam dump injection phase collisions 450 GeV 7 TeV start of the ramp Squeeze 3.5 TeV

61. J. Wenninger LNF Spring School, May 2010 LHC cycle 61  Ramp-down/pre-cycle: 1 ½ - 2 hours o Depending on initial conditions, the magnets must either be ramped down (3.5 TeV  injection) or cycled (from access).  Injection: > 15 minutes o Probe beam: low intensity bunch (≤ 10 10 p) that must be first injected when a ring is empty (safety !). Used to verify that beam parameters are OK for higher intensity. o Nominal bunch sequence follows when beam parameters have been adjusted.  Ramp: 40 minutes o Machine energy is increase at constant optics (b-function) from 450 to 3.5 TeV. For the moment the ramp rate is limited to ~1 GeV/s. o Ramp rate to nominal value ~5 GeV/s in June >> ramp will become a lot faster!  Squeeze: ~30 minutes o Injection  * is larger (10 m in IR1/5, 11 m in IR2/8) because more aperture is needed to accommodate the larger beam emittance (triplet magnets). o In the squeeze  * is reduced to its nominal physics value (presently 2 m in all IRs). This implies gradient changes of most quadrupoles in the straight sections and first part of the arc.

62. J. Wenninger LNF Spring School, May 2010 Beam squeeze 62 10 m to 2 m 30 min 11 m to 2 m Duration will soon be reduced to ~ 20 minutes

63. J. Wenninger LNF Spring School, May 2010 How equal are the IPs? 63  The  -function can be measured by exciting (shaking) the beams.  After correction of optics errors, the residual error is in a band of around +- 20% (specification). >>  * may vary from IP to IP by up to 20% ! Example of optics errors along the ring for  * 2 m (beam1) Horizontal Vertical

64. J. Wenninger LNF Spring School, May 2010 LHC cycle : physics 64  Stable beams: 10’s of hours and more… o Period with quiet running conditions for the experiments (with HV ON, etc). o Beam tuning activity reduced to the minimum (to keep good lifetimes…). o Collimators in fixed positions (they move during ramp and squeeze). o Note however that abrupt beam loss can occur in any phase due to powering problems, cooling etc etc – even in stable beams.  Experiments are protected by the collimators (shadowing), the LHC machine protection system and by their own protection system (BCM : Beam Condition Monitors). [10 30 cm -2 s -1 ]

65. J. Wenninger LNF Spring School, May 2010 Beam overlap 65  Because the beams circulate most of the time in different vacuum chambers, they also see slightly different magnetic fields. >> no guarantee that they collide at the IP ! Small beam sizes !!  To optimize the beam overlap (hor. and vert. planes) the beams are scanned across one another until the peak luminosity if found (typical +- 2 sigma). >> settings are quite reproducible – more experience needed.

66. J. Wenninger LNF Spring School, May 2010 Beam operation at 3.5 TeV  Luminosity (head on case, no crossing angle) :  The beam size s depends on  * and on beam emittance  n : Everywhere in the ring the beam size scales with 1/  ~ 1/  E. Aperture margins are reduced wrt 7 TeV !  The quench levels at 3.5 TeV are a factor ~10 higher wrt 7 TeV and the stored beam energy is lower: advantage in the early days.

67. J. Wenninger LNF Spring School, May 2010 Peak luminosity at 3.5 TeV  A consequence of the small beam size at the IP (small  *) is a large beam size in the triplet magnets.  The physical aperture in the triplet quadrupoles defines the minimum of  *. o Limits  * to ~2 m at 3.5 TeV (instead of 0.5 m at 7 TeV) Beam size  * increase by:  Factor  2 (‘naturally’ larger size)  Factor ~2 (  * limit) Luminosity loss wrt 7 TeV of:  Factor ~2  2 per plane (  *) >> overall factor ~8 for same beam intensity Lower limit on  * (with crossing angle) Present operating conditions (no crossing angle) @ 2 m

68. J. Wenninger LNF Spring School, May 2010 Intensity increase plan 68 StageN (protons)kStored E (kJ)Peak L (Hz cm-2) 3 fat pilots1.00E+103171.34E+28 4 bunches2.00E+10444.87.63E+28 4 bunches5.00E+104112.04.77E+29 8 bunches5.00E+108224.09.54E+29 4x4 bunches5.00E+1016448.01.91E+30 8x4 bunches5.00E+1032896.03.81E+30 43x435.00E+10431204.05.13E+30 8 trains of 6 b8.00E+10482150.41.33E+31 50 ns trains8.00E+10964300.82.67E+31 Assumption:  * = 2 m nominal   To gain experience with the machine protection system, 2 weeks of running time (~10 fills, 40 h of physics) must be integrated before proceeding to the next step.  Some steps require additional (machine protection) commissioning. Present phase Next step (coming days) Beams become rather dangerous

69. J. Wenninger LNF Spring School, May 2010 Performance estimate 69 charm, D’s, J/Psi Weak bosons (W, Z) 30.3 - 19.4  * 10m 1.1e10 p/bch 30.3 - 19.4  * 10m 1.1e10 p/bch 23.4 -...  * 2m 1.1e10 p/bch 23.4 -...  * 2m 1.1e10 p/bch November 7 4 coll pairs 2e10 p/bch 4 coll pairs 2e10 p/bch Apr 23 4 coll pairs 5e10 p/bch 4 coll pairs 5e10 p/bch If all goes well, we could reach L  10 32 cm -2 s -1 by November!

70. J. Wenninger LNF Spring School, May 2010 Integrated luminosity projections 70 If maintain the high availability 100 pb -1 could be integrated until November Apr 23

71. J. Wenninger LNF Spring School, May 2010 LHC operation today 71  So far LHC operation is amazingly stable and efficient (we are still in commissioning !!). But we are working with ‘tiny’ beams (on the nominal LHC scale).  In physics at the moment:  * = 2 m at IPs  *  45  m N  1.8  10 10 p/bunchk = 2 bunches  1 colliding pair / IPL  1.3  10 28 cm -2 s -1  The next step in intensity is most likely: N  4  10 10 p/bunchk = 2 bunches  1 colliding pair / IPL  6.8  10 28 cm -2 s -1  We have been able to collide bunches with nominal population (N = 10 11 ) at 450 GeV: this is a good omen for 3.5 TeV (cross fingers…) o We may be able to push luminosity faster than anticipated (L  N 2 )

72. J. Wenninger LNF Spring School, May 2010 To observe the LHC 72 http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHC1

73. J. Wenninger LNF Spring School, May 2010 Outlook 73  The LHC beam commissioning has been progressing smoothly and rapidly so far – even we are sometimes surprised !! o But the LHC remains a very complex machine, so far we operate under rather simple conditions.  The problem of the LHC: to reach ‚interesting‘ luminosities we must store very dangerous beams at a very early stage of the commissioning. o We have little operational experience. o We are still consolidating beam control software, debugging systems... o We must be sure that they are no unexpected flaws in the machine protection system (or totally unexpected situations). >> for this reason we increase the intensity/L in rather modest steps.  Assuming there are no surprises, and once we have passed the main hurdle of the initial machine protection commissioning (soon !), progress should be faster: >> so far the target of 10 31 – 10 32 cm -2 s -1 by November is within reach !

74. J. Wenninger LNF Spring School, May 2010 From darkness… …to light 74 Sept 2008 April 2010