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Rüdiger Schmidt - Februar 2006 - TU Darmstadt1 Der LHC Beschleuniger Rüdiger Schmidt - CERN Vorlesung an der Technische Universität Darmstadt 20-24 Februar.

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Presentation on theme: "Rüdiger Schmidt - Februar 2006 - TU Darmstadt1 Der LHC Beschleuniger Rüdiger Schmidt - CERN Vorlesung an der Technische Universität Darmstadt 20-24 Februar."— Presentation transcript:

1 Rüdiger Schmidt - Februar TU Darmstadt1 Der LHC Beschleuniger Rüdiger Schmidt - CERN Vorlesung an der Technische Universität Darmstadt Februar 2006 Herausforderungen LHC Beschleunigerphysik LHC Technologie Operation und Maschinenschutz Cryogenic distribution line

2 Rüdiger Schmidt - Februar TU Darmstadt 2 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 [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 - Februar TU Darmstadt events / second LHC Event

4 Rüdiger Schmidt - Februar TU Darmstadt 4 CMS Detektor

5 Rüdiger Schmidt - Februar TU Darmstadt 5 ATLAS Detektor

6 Rüdiger Schmidt - Februar TU Darmstadt 6 CERN and the LHC

7 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

8 LEP: e+e- 104 GeV/c ( ) 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

9 Rüdiger Schmidt - Februar TU Darmstadt 9 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

10 Rüdiger Schmidt - Februar TU Darmstadt 10 LHC Accelerator Physics: An Introduction Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two” accelerators in one tunnel?

11 Rüdiger Schmidt - Februar TU Darmstadt 11 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 - Februar TU Darmstadt 12 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

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

14 Rüdiger Schmidt - Februar TU Darmstadt 14 Energy loss for charged particles electrons / protons in LEP tunnel

15 Rüdiger Schmidt - Februar TU Darmstadt 15...just assuming to accelerate electrons to 7 TeV...better to accelerate protons

16 Rüdiger Schmidt - Februar TU Darmstadt 16 LHC Layout eight arcs (sectors) eight long straight section (about 700 m long) IR6: Beam dumping system IR4: RF + Beam instrumentation IR5:CMS IR1: ATLAS IR8: LHC-B IR2:ALICE Injection IR3: Momentum Cleaning (warm) IR7: Betatron Cleaning (warm) Beam dump blocks

17 Rüdiger Schmidt - Februar TU Darmstadt 17 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 rad, two particles would separate by 1 m after 10 6 m. At the LHC, with a length of 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

18 Rüdiger Schmidt - Februar TU Darmstadt 18 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)

19 Rüdiger Schmidt - Februar TU Darmstadt 19 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 [cm -1 s -2 ] LEP (e+e-) : [cm -1 s -2 ] Tevatron (p-pbar) : [cm -1 s -2 ] B-Factories: [cm -1 s -2 ]

20 Rüdiger Schmidt - Februar TU Darmstadt 20 Luminosity parameters

21 Rüdiger Schmidt - Februar TU Darmstadt 21 Beam beam interaction determines parameters Number of protons N per bunch limited to about f = Hz Beam size σ = 16  m for  = 0.5 m with one bunch N b =1 with N b = 2808 bunches (every 25 ns one bunch) L = [cm -2 s -1 ]

22 Rüdiger Schmidt - Februar TU Darmstadt 22 Large number of bunches IP l Crossing angle to avoid parasitic beam beam interaction

23 Rüdiger Schmidt - Februar TU Darmstadt 23 Large number of bunches IP l Crossing angle to avoid parasitic beam beam interaction

24 Rüdiger Schmidt - Februar TU Darmstadt 24  Total crossing angle of 300  rad  Beam size at IP 16  m, in arcs about 1 m u Beams in the arcs in two vacuum chambers Crossing angle for multibunch operation

25 Rüdiger Schmidt - Februar TU Darmstadt 25 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 cm -2 s -1 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

26 Rüdiger Schmidt - Februar TU Darmstadt 26 Very high beam current Many bunches and high energy - Energy stored in one beam about 362 MJ l Dumping the beam in a safe way l Beam induced quenches (when of beam hits magnet at 7 TeV) l Beam cleaning (Betatron and momentum cleaning)

27 Livingston type plot: Energy stored in the beam courtesy R.Assmann Transverse energy density: even a factor of 1000 larger

28 Rüdiger Schmidt - Februar TU Darmstadt 28 LHC accelerator in the tunnel LHC Main Systems Superconducting magnets Cryogenics Vacuum system Powering (industrial use of High Temperature Superconducting material)

29 Rüdiger Schmidt - Februar TU Darmstadt main dipoles multipole corrector magnets 392 main quadrupoles corrector magnets Regular arc: Magnets

30 Rüdiger Schmidt - Februar TU Darmstadt 30 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

31 Rüdiger Schmidt - Februar TU Darmstadt 31 Insulation vacuum for the cryogenic distribution line Regular arc: Vacuum Insulation vacuum for the magnet cryostats Beam vacuum for Beam 1 + Beam 2

32 Rüdiger Schmidt - Februar TU Darmstadt 32 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)

33 Rüdiger Schmidt - Februar TU Darmstadt Dipolmagnets Length about 15 m Magnetic Field 8.3 T Two beam tubes with an opening of 56 mm Dipole magnets for the LHC

34 Rüdiger Schmidt - Februar TU Darmstadt 34 Coils for Dipolmagnets 15 m long

35 Rüdiger Schmidt - Februar TU Darmstadt 35 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 = Ampere L = 15 m F = 165 tons 56 mm

36 Rüdiger Schmidt - Februar TU Darmstadt 36 Beam tubes Supraconducting coil Nonmagetic collars Ferromagnetic iron Steelcylinder for Helium Insulationvacuum Supports Vacuumtank

37 Rüdiger Schmidt - Februar TU Darmstadt 37 First cryodipole lowered on 7 March 2005 Only one access point for 15 m long dipoles, 35 tons each

38 Rüdiger Schmidt - Februar TU Darmstadt 38 Transport in the tunnel with an optical guided vehicle about 1600 magnets to be transported for 15 km at 3 km/hour

39 Rüdiger Schmidt - Februar TU Darmstadt 39 Operation and machine protection

40 Rüdiger Schmidt - Februar TU Darmstadt 40 energy ramp preparation and access injection phase coast LHC magnetic cycle L.Bottura 450 GeV 7 TeV start of the ramp

41 Rüdiger Schmidt - Februar TU Darmstadt 41 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

42 Rüdiger Schmidt - Februar TU Darmstadt 42 SPS experiment: Beam damage at 450 GeV Controlled SPS experiment l 8  protons clear damage l beam size σ x/y = 1.1mm/0.6mm above damage limit l 2  protons below damage limit 6 cm 25 cm 0.1 % of the full LHC beams V.Kain et al

43 Rüdiger Schmidt - Februar TU Darmstadt 43 Regular (very healthy) operation Assuming that the beams are colliding at 7 TeV Single beam lifetime larger than 100 hours….. Collision of beams with a luminosity of 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)

44 Rüdiger Schmidt - Februar TU Darmstadt 44 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 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

45 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

46 Rüdiger Schmidt - Februar TU Darmstadt 46 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

47 Rüdiger Schmidt - Februar TU Darmstadt 47 Full LHC beam deflected into copper target Target length [cm] vaporisation melting N.Tahir (GSI) et al. Copper target 2 m Energy density [GeV/cm 3 ] on target axis 2808 bunches

48 Rüdiger Schmidt - Februar TU Darmstadt 48 Density change in target after impact of 100 bunches Energy deposition calculations using FLUKA Numerical simulations of the hydrodynamic and thermodynamic response of the target with two- dimensional hydrodynamic computer code Target radial coordinate [cm] radial copper solid state N.Tahir (GSI) et al. 100 bunches – target density reduced to 10%

49 Rüdiger Schmidt - Februar TU Darmstadt 49 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

50 Rüdiger Schmidt - Februar TU Darmstadt 50 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

51 Rüdiger Schmidt - Februar TU Darmstadt 51 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

52 Rüdiger Schmidt - Februar TU Darmstadt 52 Beam Dump Block - Layout about 8 m L.Bruno concrete shielding beam absorber (graphite)

53 Rüdiger Schmidt - Februar TU Darmstadt 53 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

54 Rüdiger Schmidt - Februar TU Darmstadt 54 L.Bruno: Thermo-Mechanical Analysis with ANSYS Temperature of beam dump block at 80 cm inside up to C

55 Rüdiger Schmidt - Februar TU Darmstadt 55 Protection and Beam Energy A small fraction of beam sufficient for damage Very efficient protection systems throughout the cycle are required A tiny fraction of the beam is sufficient to quench a magnet Very efficient beam cleaning is required Sophisticated beam cleaning with about 50 collimators, each with two jaws, in total about 90 collimators and beam absorbers Collimators are close to the beam (full gap as small as 2.2 mm, for 7 TeV with fully squeezed beams), particles will always touch collimators first !

56 Rüdiger Schmidt - Februar TU Darmstadt  ~1.3 mm Beam +/- 3 sigma 56.0 mm Beam in vacuum chamber with beam screen at 7 TeV

57 Rüdiger Schmidt - Februar TU Darmstadt 57 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

58 Rüdiger Schmidt - Februar TU Darmstadt 58 The LHC Phase 1 Collimator Vacuum tank with two jaws installed Designed for maximum robustness: Advanced Carbon Composite material for the jaws with water cooling! R.Assmann et al

59 Rüdiger Schmidt - Februar TU Darmstadt 59 RF contacts for guiding image currents Beam spot 2 mm

60 Rüdiger Schmidt - Februar TU Darmstadt 60 Conclusions

61 Rüdiger Schmidt - Februar TU Darmstadt 61 Recalling LHC challenges l Enormous amount of equipment l Complexity of the LHC accelerator l New challenges in accelerator physics with LHC beam parameters pushed to the extreme Fabrication of equipment Installation LHC Beam commissioning LHC “hardware” commissioning

62 Rüdiger Schmidt - Februar TU Darmstadt 62 Conclusions 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 l No one has ny 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 L.Evans

63 Rüdiger Schmidt - Februar TU Darmstadt 63 Acknowledgement The LHC accelerator is being realised by CERN supported by the member states, in collaboration with institutes from many countries over a period of more than 20 years Many 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

64 Rüdiger Schmidt - Februar TU Darmstadt 64 Some references Accelerator physics l Proceedings of CERN ACCELERATOR SCHOOL (CAS), 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 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

65 Rüdiger Schmidt - Februar TU Darmstadt 65 Autumn 2004 The CERN accelerator complex: injectors and transfer 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 TI8 TI2 Ions protons Beam 1 Beam 2 Beam size of protons decreases with energy:  2 = 1 / E Beam size large at injection Beam fills vacuum chamber at 450 GeV

66 Rüdiger Schmidt - Februar TU Darmstadt 66 Kugelstossen: The energy of one shot (5 kg) at 800 km/hour corresponds to the energy stored in one bunch at 7 TeV. There are 2808 bunches. Factor 200 compared to HERA, TEVATRON and SPS. shot Energy stored in one beam at 7 TeV: 362 MJoule

67 Rüdiger Schmidt - Februar TU Darmstadt 67 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: K, 6T Für 10 T, Operation less than 1.9 K required Copyright A.Verweij


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