1. Rüdiger Schmidt - Wuppertal Januar 20041 Der LHC Beschleuniger Rüdiger Schmidt - CERN Universität Wuppertal Januar 2004 Herausforderungen LHC Beschleunigerphysik LHC Technologie Operation und Maschinenschutz

2. Rüdiger Schmidt - Wuppertal Januar 20042 Energy and Luminosity l Particle physics requires an accelerator colliding beams with a centre-of-mass energy substantially exceeding 1TeV l In order to observe rare events, the luminosity should be in the order of 10 34 [cm -1 s -2 ] (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.... )

3. Rüdiger Schmidt - Wuppertal Januar 20043 10 9 events / second LHC Event

4. Rüdiger Schmidt - Wuppertal Januar 20044 CERN and the LHC

5. CERN is the leading European institute for particle physics It is close to Geneva across the French Swiss border There are 20 CERN member states, 5 observer states, and many other states participating in research LHC CMS ATLAS

6. LEP: e+e- 104 GeV/c (1989-2000) Circumference 26.8 km LHC proton-proton Collider 7 TeV/c in the LEP tunnel 2 rings Injection from SPS at 450 GeV/c ATLAS CMS

7. Rüdiger Schmidt - Wuppertal Januar 20047 LHC: From first ideas to realisation 1982 : First studies for the LHC project 1983 : Z0 detected at SPS proton antiproton collider 1985 : Nobel Price for S. van der Meer and C. Rubbia 1989 : Start of LEP operation (Z-factory) 1994 : Approval of the LHC by the CERN Council 1996 : Final decision to start the LHC construction 1996 : LEP operation at 100 GeV (W-factory) 2000 : End of LEP operation 2002 : LEP equipment removed 2003 : Start of the LHC installation 2005 : Start of hardware commissioning 2007 : Commissioning with beam planned

8. Rüdiger Schmidt - Wuppertal Januar 20048 To make the LHC accelerator a reality: Accelerators physics and.... l Electromagnetism und Relativity l Thermodynamics l Mechanics l Quantum mechanics l Physics of nonlinear systems l Solid state physics und surface physics l Particle physics and radiation physics l Vacuum physics + Engineering Mechanical, Civil, Cryogenics, Electrical, Automation, Computing

9. l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l LHC Parameters l The CERN accelerator complex: injectors and transfer l LHC technology l LHC Operation and machine protection l Conclusions Outline

10. l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l Wrapping up: LHC Parameters l The CERN accelerator complex: injectors and transfer l LHC technology l LHC Operation and machine protection l Conclusions Outline

11. Rüdiger Schmidt - Wuppertal Januar 200411 Particle acceleration Acceleration of a charged particle by an electrical potential Energy gain given by the potential l For an acceleration to 7 TeV a voltage of 7 TV is required l The maximum electrical field in an accelerator is in the order of some 10 MV/m (superconducting RF cavities) l To accelerate to 7 TeV would require a linear accelerator with a length of about 350 km (assuming 20 MV/m)

12. Rüdiger Schmidt - Wuppertal Januar 200412 Acceleration in a cavity U = 1000000 V d = 1 m q = e 0  E = 1 MeV - +

13. Rüdiger Schmidt - Wuppertal Januar 200413 How to get to 7 TeV: Synchrotron – circular accelerator and many passages in RF cavities LINAC (planned for several hundred GeV - but not above 1 TeV) LHC circular machine with energy gain per turn some MeV

14. Rüdiger Schmidt - Wuppertal Januar 200414 RF systems: 400 MHz 400 MHz system: all 16 sc cavities (copper sputtered with niobium) for 16 MV/beam were built and assembled in four modules Power test of the first module

15. Rüdiger Schmidt - Wuppertal Januar 200415 Particle deflection: Lorentz Force The force on a charged particle is proportional to the charge, and to the vector product of velocity and magnetic field: Maximaler Impuls 7000 GeV/c Radius 2805 m Ablenkfeld B = 8.33 Tesla Magnetfeld mit Eisenmagneten maximal 2 tesla, daher werden supraleitende Magnete benötigt z x s v B F

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

17. Rüdiger Schmidt - Wuppertal Januar 200417 Energy loss for charged particles electrons / protons in LEP tunnel

18. Rüdiger Schmidt - Wuppertal Januar 200418...just assuming to accelerate electrons to 7 TeV...better to accelerate protons

19. l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l The CERN accelerator complex: injectors and transfer l Wrapping up: LHC Parameters l LHC technology l LHC operation and machine protection l Conclusions Outline

20. LHC: eight arcs (approximatley circular) and eight long straight section (about 700 m long) Momentum Cleaning Betatron Cleaning Beam dump system RF + Beam instrumentation CMS ATLAS LHC-B ALICE

21. Rüdiger Schmidt - Wuppertal Januar 200421 CMS Detektor

22. Rüdiger Schmidt - Wuppertal Januar 200422 Beam transport Need for keeping 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 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 l Particles would „drop“ due to gravitation

23. Rüdiger Schmidt - Wuppertal Januar 200423 The LHC arcs: FODO cells u Dipole- und Quadrupol magnets –Particle trajectory stable for particles with nominal momentum u Sextupole magnets –To correct the trajectories for off momentum particles –Particle trajectories stable for small amplitudes (about 10 mm) u Multipole-corrector magnets –Sextupole - and decapole corrector magnets at end of dipoles –Particle trajectories can become instable after many turns (even after, say, 10 6 turns)

24. Rüdiger Schmidt - Wuppertal Januar 200424 Particle stability and supraconducting 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

25. Rüdiger Schmidt - Wuppertal Januar 200425 Dynamic aperture and magnet imperfections l Particles with small amplitudes are in general stable l Particles with large amplitudes are not stable l The dynamic aperture is the limit of the stability region l The dynamic aperture depends on field error - without any field errors, the dynamic aperture would be large l The magnets should be made such as the dynamic aperture is not too small (say, 10  the amplitude of a one sigma particle, assuming Gaussian distribution) l The dynamic aperture depends also on the working point and on the sextupole magnets for correction of chromatic effects

26. l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l Wrapping up: LHC Parameters l The CERN accelerator complex: injectors and transfer l LHC technology l LHC operation and machine protection l Conclusions Outline

27. Rüdiger Schmidt - Wuppertal Januar 200427 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 -1 s -2 ] LEP (e+e-) : 3-4 10 31 [cm -1 s -2 ] Tevatron (p-pbar) : 3 10 31 [cm -1 s -2 ] B-Factories: 10 34 [cm -1 s -2 ]

28. Rüdiger Schmidt - Wuppertal Januar 200428 Luminosity parameters What happens with one particle experiencing the force of the em-fields or 10 11 protons in the other beam during the collision ?

29. l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l Wrapping up: LHC Parameters l The CERN accelerator complex: injectors and transfer l LHC technology l LHC operation and machine protection l Conclusions Outline

30. Rüdiger Schmidt - Wuppertal Januar 200430 Limitation: beam-beam interaction Bunch intensity limited due to this strong non- linearity to about N = 10 11

31. Rüdiger Schmidt - Wuppertal Januar 200431 Beam beam interaction determines parameters Beam size 16  m, for  = 0.5 m f = 11246 Hz Beam size given by injectors and by space in vacuum chamber Number of protons per bunch limited to about 10 11 L = N 2 f n b / 4   x  y = 3.5 10 30 [cm -2 s -1 ] with one bunch with 2808 bunches (every 25 ns one bunch) L = 10 34 [cm -2 s -1 ]

32. l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l Wrapping up: LHC Parameters l The CERN accelerator complex: injectors and transfer l LHC technology l LHC operation and machine protection l Conclusions Outline

33. Rüdiger Schmidt - Wuppertal Januar 200433 Large number of bunches IP l Crossing angle to avoid long range beam beam interaction

34. Rüdiger Schmidt - Wuppertal Januar 200434 Large number of bunches IP l Crossing angle to avoid long range beam beam interaction

35. Rüdiger Schmidt - Wuppertal Januar 200435 Large number of bunches IP l Crossing angle to avoid long range beam beam interaction

36. Rüdiger Schmidt - Wuppertal Januar 200436 u Focusing quadrupole for beam 1, defocusing for beam 2 u High gradient quadrupole magnets with large aperture (US-JAPAN)  Total crossing angle of 300  rad  Beam size at IP 16  m, in arcs about 1 mm Crossing angle for multibunch operation

37. Rüdiger Schmidt - Wuppertal Januar 200437 Layout of insertion for ATLAS and CMS

38. l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l The CERN accelerator complex: injectors and transfer l LHC Parameters l LHC technology l LHC operation and machine protection l Conclusions Outline

39. Rüdiger Schmidt - Wuppertal Januar 200439 summarising constraints and consequences…. Centre-of-mass energy must well exceed 1 TeV, LHC installed into LEP tunnel l Colliding protons, and also heavy ions l Magnetic field of 8.3 T with superconducting magnets l Large amount of energy stored in magnets Luminosity of 10 34 l Need for “two accelerators” in one tunnel with beam parameters pushed to the extreme – with opposite magnetic dipole field l Large amount of energy stored in beams Economical constraints and limited space l Two-in-one superconducting magnets

40. Rüdiger Schmidt - Wuppertal Januar 200440 Very high beam current Many bunches and high energy - Energy in one beam about 330 MJ l Beam stability and magnet field quality l Synchrotron radiation - power to cryogenic system l Dumping the beam in a safe way l Beam induced quenches (when 10 -7 of beam hits magnet at 7 TeV) l Beam cleaning (Betatron and momentum cleaning) l Radiation, in particular in experimental areas from beam collisions (beam lifetime is dominated by this effect) l Photo electrons - accelerated by the following bunches

41. Rüdiger Schmidt - Wuppertal Januar 200441 Challenges: Energy stored in the beam courtesy R.Assmann Momentum [GeV/c] Energy stored in the beam [MJ] Transverse energy density: even a factor of 1000 larger x 200 x 10000 One beam, nominal intensity (corresponds to an energy that melts 500 kg of copper)

42. Rüdiger Schmidt - Wuppertal Januar 200442 l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l Wrapping up: LHC Parameters l The CERN accelerator complex: injectors and transfer l LHC technology l LHC operation and machine protection l Conclusions Outline

43. Rüdiger Schmidt - Wuppertal Januar 200443 Getting beam into the LHC Beam size of protons decreases with energy:  2 = 1 / E l Beam size large at injection l Beam fills vacuum chamber at 450 GeV If the energy would be lower... l larger vacuum chamber and larger magnets – increased cost l magnets and power converter limitations (dynamic effects, stability, …) l issues of beam stability Injection from the SPS at 450 GeV, via two transfer lines, into the LHC

44. Rüdiger Schmidt - Wuppertal Januar 200444 Autumn 2004 Injector complex High intensity beam from the SPS into LHC at 450 GeV via TI2 and TI8 LHC accelerates to 7 TeV LEIR CPS SPS Booster LINACS LHC 3 4 5 6 7 8 1 2 TI8 TI2 Ions protons Extraction Beam 1 Beam 2 Summer 2003 Spring 2006

45. Rüdiger Schmidt - Wuppertal Januar 200445 Injector Complex l Already today, beams are available close to the nominal beam parameters required for the LHC l Fast extraction from the SPS with a new system into a new line successfully done in summer 2003 B.Goddard

46. Rüdiger Schmidt - Wuppertal Januar 200446 l Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel? l LHC Layout l The quest for high luminosity and the consequences l Beam-Beam interaction l Crossing angle and insertion layout l Wrapping up: LHC Parameters l The CERN accelerator complex: injectors and transfer l LHC technology l LHC operation and machine protection l Conclusions Outline

47. Rüdiger Schmidt - Wuppertal Januar 200447 LHC accelerator in the tunnel LHC Main Systems Superconducting magnets Cryogenics Vacuum system Powering (industrial use of High Temperature Superconducting material)

48. Rüdiger Schmidt - Wuppertal Januar 200448 1232 main dipoles + 3700 multipole corrector magnets 392 main quadrupoles + 2500 corrector magnets Regular arc: Magnets

49. Rüdiger Schmidt - Wuppertal Januar 200449 Regular arc: Cryogenics Supply and recovery of helium with 26 km long cryogenic distribution line Static bath of superfluid helium at 1.9 K in cooling loops of 110 m length Connection via service module and jumper

50. Rüdiger Schmidt - Wuppertal Januar 200450 Insulation vacuum for the cryogenic distribution line Regular arc: Vacuum Insulation vacuum for the magnet cryostats Beam vacuum for Beam 1 + Beam 2

51. Rüdiger Schmidt - Wuppertal Januar 200451 Regular arc: Electronics Along the arc about several thousand electronic crates (radiation tolerant) for: quench protection, power converters for orbit correctors and instrumentation (beam, vacuum + cryogenics)

52. Rüdiger Schmidt - Wuppertal Januar 200452 Installation of cryogenic distribution line in the LHC tunnel – started during summer 2003

53. Rüdiger Schmidt - Wuppertal Januar 200453 1232 Dipolmagnets Length about 15 m Magnetic Field 8.3 T Two beam tubes with an opening of 56 mm Dipole magnets for the LHC

54. Rüdiger Schmidt - Wuppertal Januar 200454 Coils for Dipolmagnets

55. Rüdiger Schmidt - Wuppertal Januar 200455 Superconducting cable for 12 kA 15 mm / 2 mm Temperature 1.9 K cooled with Helium Force on the cable: F = B * I0 * L with B = 8.33 T I0 = 12000 Ampere L = 15 m F = 165 tons 56 mm

56. Rüdiger Schmidt - Wuppertal Januar 200456 Beam tubes Supraconducting coil Nonmagetic collars Ferromagnetic iron Steelcylinder for Helium Insulationvacuum Supports Vacuumtank

57. Rüdiger Schmidt - Wuppertal Januar 200457 Magnetic field - current density - temperature Superconducting material determines: Tc critical temperature Bc critical field Production process: Jc critical current density Bc Tc Lower temperature  increased current density Typical for NbTi: 2000 A/mm2 @ 4.2K, 6T Für 10 T, Operation less than 1.9 K required Copyright A.Verweij

58. Rüdiger Schmidt - Wuppertal Januar 200458 Supraconducting wire  1 mm  6  m Typical value for operation at 8 T and 1.9 K: 800 A Copyright A.Verweij Rutherford cable width 15 mm

59. Rüdiger Schmidt - Wuppertal Januar 200459 Dipole magnet production: Snapshot at industry L.Rossi

60. Rüdiger Schmidt - Wuppertal Januar 200460 Storage of dipole cold masses waiting for cryostating

61. Rüdiger Schmidt - Wuppertal Januar 200461 Performance of LHC dipole magnets

62. Rüdiger Schmidt - Wuppertal Januar 200462 Challenges for dipole production l The magnets must reach without quenching a field of at least 8.3 Tesla, and possibly 9 Tesla l The field quality must be excellent (relative field errors much less than 0.1 %, positioning of collars to some 10  m) l The geometry must be respected – and the magnet must be correctly bent l All magnets must be produced in time, delivered to CERN, installed in the cryostats, cold tested, and finally installed into the LHC tunnel

63. Rüdiger Schmidt - Wuppertal Januar 200463 Operation and machine protection

64. Rüdiger Schmidt - Wuppertal Januar 200464 Outline l Energy stored in the LHC magnets and beams l Charging the energy l LHC dipole magnets - discharging the energy irregular discharge - magnet quenches l LHC Beams - discharging the energy regular and irregular discharge l Magnets facing Beams

65. Rüdiger Schmidt - Wuppertal Januar 200465 Energy stored in dipole magnets 10 GJoule…… l corresponds to the energy of 1900 kg TNT l corresponds to the energy of 400 kg Chocolate l corresponds to the energy for heating and melting 12000 kg of copper Could this damage equipment: How fast can this energy be released? E dipole = 0.5  L dipole  I 2 dipole Energy stored in one dipole is 7.6 MJoule For all 1232 dipoles in the LHC: 9.4 GJ

66. Rüdiger Schmidt - Wuppertal Januar 200466 Outline l Energy stored in the LHC magnets and beams l Charging the energy l LHC dipole magnets - discharging the energy irregular discharge - magnet quenches l LHC Beams - discharging the energy regular and irregular discharge l Magnets facing Beams

67. Rüdiger Schmidt - Wuppertal Januar 200467 energy ramp preparation and access injection phase coast LHC magnetic cycle L.Bottura 450 GeV 7 TeV start of the ramp

68. Rüdiger Schmidt - Wuppertal Januar 200468 injection phase 12 batches from the SPS (every 20 sec) one batch 216 / 288 bunches LHC magnetic cycle - Beam injection L.Bottura 450 GeV 7 TeV beam dump

69. Rüdiger Schmidt - Wuppertal Januar 200469 Outline l Energy stored in the LHC magnets and beams l Charging the energy l LHC dipole magnets - discharging the energy irregular discharge - magnet quenches l LHC Beams - discharging the energy regular and irregular discharge l Magnets facing Beams

70. Rüdiger Schmidt - Wuppertal Januar 200470 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

71. Rüdiger Schmidt - Wuppertal Januar 200471 Quench - transition from superconducting state to normalconducting state Quenches are initiated by an energy in the order of mJ (corresponds to the energy of 1000 protons at 7 TeV) l Movement of the superconductor by several  m (friction and heat dissipation) l Beam losses l Failure in cooling To limit the temperature increase after a quench (in 1s to 5000 K) l The quench has to be detected l The energy is distributed in the magnet by force-quenching the coils using quench heaters l The magnet current has to be switched off within << 1 second

72. Rüdiger Schmidt - Wuppertal Januar 200472 Outline l Energy stored in the LHC magnets and beams l Charging the energy l LHC dipole magnets - discharging the energy irregular discharge - magnet quenches l LHC Beams - discharging the energy regular and irregular discharge l Magnets facing Beams

73. Rüdiger Schmidt - Wuppertal Januar 200473 Regular (very healthy) operation Assuming that the beams are colliding at 7 TeV Single beam lifetime larger than 100 hours….. corresponds to a loss of about 1 kW / beam far below the cooling power of the cryogenic system, even if all particles would be lost at 1.9 K losses should be either distributed across the machine or captured in the warm cleaning insertions Collision of beams with a luminosity of 10 34 cm -2 s -1 lifetime of the beam can be be dominated by collisions 10 9 protons / second lost per beam / per experiment (in IR 1 and IR 5 - high luminosity insertions) - this is about 1.2 kW large heat load to close-by superconducting quadrupoles heavy shielding around the high luminosity IPs

74. Rüdiger Schmidt - Wuppertal Januar 200474 End of data taking in normal operation l Luminosity lifetime estimated to be approximately 10 h (after 10 hours only 1/3 of initial luminosity) l Beam current somewhat reduced - but not much l Energy per beam still about 200-300 MJ l Beams are extracted in beam dump blocks l The only component that can stand a fast loss of the full beam at top energy is the beam dump block - all other components would be damaged l At 7 TeV, fast beam losses with an intensity of about 5% of a “nominal bunch” could damage superconducting coils

75. Rüdiger Schmidt - Wuppertal Januar 200475 LHC ring: 3 insertions for machine protection systems Beam Cleaning IR3 (Momentum) Beam Cleaning IR7 (Betatron) Beam dump system IR6 RF+ Beam monitors IR4

76. Rüdiger Schmidt - Wuppertal Januar 200476 Beam losses into material l Proton losses lead to particle cascades in materials l The energy deposition leads to a temperature increase l For the maximum energy deposition as a function of material there is no straightforward expression l Programs such as FLUKA are being used for the calculation of the energy deposition Magnets could quench….. beam lost - re-establish condition will take hours The material could be damaged….. melting losing their performance (mechanical strength) Repair could take several weeks

77. Rüdiger Schmidt - Wuppertal Januar 200477 Damage of material for impact of a pencil beam copper graphite

78. Rüdiger Schmidt - Wuppertal Januar 200478 Schematic layout of beam dump system in IR6 Q5R Q4R Q4L Q5L Beam 2 Beam 1 Beam Dump Block Septum magnet deflecting the extracted beam H-V kicker for painting the beam about 700 m about 500 m Fast kicker magnet

79. Rüdiger Schmidt - Wuppertal Januar 200479 Beam Dump Block - Layout about 8 m L.Bruno concrete shielding beam absorber (graphite)

80. Rüdiger Schmidt - Wuppertal Januar 200480 Beam on Beam Dump Block about 35 cm M.Gyr initial transverse beam dimension in the LHC about 1 mm beam is blown up due to long distance to beam dump block additional blow up due to fast dilution kickers: painting of beam on beam dump block beam impact within less than 0.1 ms

81. Rüdiger Schmidt - Wuppertal Januar 200481 L.Bruno: Thermo-Mechanical Analysis with ANSYS Temperature of beam dump block at 80 cm inside up to 800 0 C

82. Rüdiger Schmidt - Wuppertal Januar 200482 Outline l Energy stored in the LHC magnets and beams l Charging the energy l LHC dipole magnets - discharging the energy irregular discharge - magnet quenches l LHC Beams - discharging the energy regular and irregular discharge l Magnets facing Beams

83. Rüdiger Schmidt - Wuppertal Januar 200483 Beam lifetime with nominal intensity at 7 TeV Beam lifetime Beam power into equipment (1 beam) Comments 100 h1 kWHealthy operation 10 h10 kWOperation acceptable, collimation must absorb large fraction of beam energy (approximately beam losses = cryogenic cooling power at 1.9 K) 0.2 h500 kWOperation only possibly for short time, collimators must be very efficient 1 min6 MWEquipment or operation failure - operation not possible - beam must be dumped << 1 min> 6 MWBeam must be dumped VERY FAST Failures will be a part of the regular operation and MUST be anticipated

84. Rüdiger Schmidt - Wuppertal Januar 200484 +- 3  ~5 mm Beam +/- 3 sigma 56.0 mm Beam in vacuum chamber with beam screen at 450 GeV

85. Rüdiger Schmidt - Wuppertal Januar 200485 +- 3  ~1.3 mm Beam +/- 3 sigma 56.0 mm Beam in vacuum chamber with beam screen at 7 TeV

86. Rüdiger Schmidt - Wuppertal Januar 200486 Beam+/- 3 sigma 56.0 mm 1 mm +/- 8 sigma = 4.0 mm Example: Setting of collimators at 7 TeV - with luminosity optics Beam must always touch collimators first ! R.Assmanns EURO Collimators at 7 TeV, squeezed optics

87. Rüdiger Schmidt - Wuppertal Januar 200487 Jaws (blocks of solid materials such as copper, graphite, ….) very close to the beam to absorb more than 99.9 % of protons that would be lost Primary collimators:Intercept primary halo Impact parameter: ~ 1  m Scatter protons of primary halo Convert primary halo to secondary off-momentum halo Secondary collimators:Intercept secondary halo Impact parameter: ~ 200  m Absorb most protons Leak a small tertiary halo Particles Beam axis Impact parameter Collimator jaw Basic concept of two stage collimation R.Assmann / J.B.Jeanneret

88. Rüdiger Schmidt - Wuppertal Januar 200488 Accidental kick by the beam dump kicker at 7 TeV part of beam touches collimators (about 20 bunches from 2800) P.Sievers / A.Ferrari / V.Vlachoudis circulating beam

89. Rüdiger Schmidt - Wuppertal Januar 200489 Accidental kick by the beam dump kicker at 7 TeV part of beam touches collimators (about 20 bunches from 2800) P.Sievers / A.Ferrari / V. Vlachoudis Beryllium

90. Rüdiger Schmidt - Wuppertal Januar 200490 Optimisation of Cleaning system l Requirements for collimation system take into account failure scenarios and imperfect operation Worst case is the impact of about 20 bunches on the collimator due to pre-firing of one dump kicker module l Material for collimator is being reconsidered - low Z material is favoured l Impedance to be considered - conducting material is favoured l More exotic materials are considered: copper loaded graphite, beryllium, partially plated copper ….

91. Rüdiger Schmidt - Wuppertal Januar 200491 Conclusions

92. Rüdiger Schmidt - Wuppertal Januar 200492 Recalling LHC challenges l Enormous amount of equipment l Complexity of the LHC accelerator l New challenges in accelerator physics with LHC beam parameters 20052004 1 2 3 4 5 6 7 8 9 10 11 12 20062007 1 2 3 4 5 6 7 8 9 10 11 12 Fabrication of equipment Installation Beam in one sectorLHC Beam commissioning LHC “hardware” commissioning

93. Rüdiger Schmidt - Wuppertal Januar 200493 Conclusions The LHC is installed and commissioned in eight (rather) independent sectors - that allows for activities to be performed in parallel …….... to avoid a lengthy and painful start-up when LHC hardware ready for two beam l The LHC is a global project with the world-wide high- energy physics community devoted to its progress and results l As a project, it is much more complex and diversified than the SPS or LEP or any other large accelerator project constructed to date Machine Advisory Committee, chaired by Prof. M. Tigner, March 2002

94. Rüdiger Schmidt - Wuppertal Januar 200494 citing Lyn Evans l No one has any doubt that it will be a great challenge for both machine to reach design luminosity and for the detectors to swallow it. l However, we have a competent and experienced team, and 30 years of accumulated knowledge from previous CERN projects has been put into the LHC design

95. Rüdiger Schmidt - Wuppertal Januar 200495 Acknowledgement The LHC accelerator is being realised by CERN in collaboration with institutes from many countries over a period of more than 20 years Main contribution come from the USA, Russia, India, Canada, special contributions from France and Switzerland Industry plays a major role in the construction of the LHC Thanks for the material from: R.Assmann, L.Bottura, L.Bruno, R.Denz, A.Ferrari, B.Goddard, M.Gyr, D.Hagedorn, J.B.Jeanneret, P.Proudlock, B.Puccio, F.Rodriguez-Mateos, F.Ruggiero, L.Rossi, S.Russenschuck, P.Sievers, G.Stevenson, A.Verweij, V.Vlachoudis, L.Vos

96. Rüdiger Schmidt - Wuppertal Januar 200496 Some references Accelerator physics l Proceedings of CERN ACCELERATOR SCHOOL (CAS), http://schools.web.cern.ch/Schools/CAS/CAS_Proceedings.html http://schools.web.cern.ch/Schools/CAS/CAS_Proceedings.html In particular: 5th General CERN Accelerator School, CERN 94-01, 26 January 1994, 2 Volumes, edited by S.Turner Superconducting magnets / cryogenics l Superconducting Accelerator Magnets, K.H.Mess, P.Schmüser, S.Wolff, World Scientific 1996 l Superconducting Magnets, M.Wilson, Oxford Press l Superconducting Magnets for Accelerators and Detectors, L.Rossi, CERN-AT- 2003-002-MAS (2003) LHC l Technological challenges for the LHC, CERN Academic Training, 5 Lectures, March 2003 (CERN WEB site) l Beam Physics at LHC, L.Evans, CERN-LHC Project Report 635, 2003 l Status of LHC, R.Schmidt, CERN-LHC Project Report 569, 2003 l...collimation system.., R.Assmann et al., CERN-LHC Project Report 640, 2003 l LHC Design Report 1995 l LHC Design Report 2003 - in preparation

97. Rüdiger Schmidt - Wuppertal Januar 200497 Power into superconducting cable after a quench

98. Rüdiger Schmidt - Wuppertal Januar 200498 F.Rodriguez-Mateos, K.Dahlerup-Petersen Energy extraction system in LHC tunnel Resistors absorbing the energy Switches - for switching the resistors into series with the magnets