LHC Commissioning and First Operation

Transcription

1 LHC Commissioning and First Operation PPC 2010, July 12, 2010, Turin, Italy Steve Myers Director for Accelerators and Technology, CERN Geneva (On behalf of the LHC team and international collaborators)

2 Topics The LHC(reminder) The last 18 months (rapidly) The Accident The Repair and consolidation Initial Commissioning Present status and plans

3 The LHC Superconducting Proton Accelerator and Collider installed in a 27km circumference underground tunnel (tunnel crosssection diameter 4m) at CERN Tunnel was built for LEP collider in 1985 S. Myers QUB March 11,

4 LHC: Some Technical Challenges Circumference (km) m underground Number of superconducting twin-bore Dipoles Length of Dipole (m) Cable Nb-Ti, cold mass 37million kg Dipole Field Strength (Tesla) 8.4 Results from the high beam energy needed Operating Temperature (K) (cryogenics system) 1.9 Superconducting magnets needed for the high magnetic field Super-fluid helium Current in dipole sc coils (A) Results from the high magnetic field 1ppm resolution Beam Intensity (A) loss causes quench Beam Stored Energy (MJoules) 362 Results from high beam energy and high beam current 1MJ melts 1.5kg Cu Magnet Stored Energy (MJoules)/octant 1100 Results from the high magnetic field Sector Powering Circuit different electrical circuits

5 Interconnections During cool-down of the LHC the machine contracts by 80 metres, 10m per octant Vacuum continuity Electrical connections S. Myers QUB March 11,

6 Accident of September 19 th 2008 Following a very impressive start-up with beam on September 10, 2008 During a few days period without beam Making the last step of dipole circuit in sector 34, to 9.3kA At 8.7kA, development of resistive zone in the dipole bus bar splice between Q24 R3 and the neighbouring dipole Electrical arc developed which punctured the helium enclosure 6

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8 Bus bar splice 8

9 Fault tree [1/3] Observed on magnet Absence of soldering No sensitive detection on bus bar Resistance 220 nohm Bad contact with stabilizer Electro-thermal model Thermal runaway Meltdown, open circuit Power converter fast discharge Electrical arc

10 Fault tree [2/3] Electrical arc He vessel perforation Beam pipe perforation Soot He discharge in insulation vacuum Inadequate sizing of relief devices (MCI) Loss of beam vacuum Contamination by soot Blast ODH in tunnel Mechanical damage to MLI Pressurization of vacuum enclosures Trip AUG Break vent door Contamination by MLI

11 Fault tree [3/3] Pressurization of vacuum enclosures Pressure forces on vacuum barriers Plastic deformation of shells Used to estimate max pressure reached Buckling of bellows Rupture of supports and ground anchors Displacement of magnets Damage to tunnel floor Mechanical damage to interconnects Secondary electrical arcs

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13 Consequences 13

14 Electrical arc between C24 and Q24 V lines M3 line

15 Collateral damage: secondary arcs QBBI.B31R3 M3 line QQBI.27R3 M3 line

16 16

17 Phase cryogenics!

18 Current in the Dipoles as function of time Pyramid for Splice Mapping Maya Pyramid

19 Splice Mapping of Quadrupoles QPS team 1nΩ

20 A78.RB: Normalized Bus Segment Resistance 1nΩ Every single sc splice were measured in

21 Decided Scenario Run at 3.5 TeV/beam up to a integrated luminosity of around 1fb -1. Then consolidate the whole machine for 7TeV/beam (during a shutdown in 2012) From 2013 onwards LHC will be capable of maximum energies and luminosities

22 Why are we limiting the beam energy to 3.5TeV in ? All the work we have done since November 2008 makes us certain that a repeat of September 19 can NEVER happen. The offending connector in this incident had an estimated resistance of 220nΩ. We have measured all 10,000 inter-magnet connectors and the maximum resistance we have seen is 2.8nΩ. BUT in April 2009, we have uncovered a different possible failure scenario which could under certain circumstances produce an electric arc in the copper stabilizers of the magnet interconnects 22

23 First Collisions at 7TeV cm March 30, 2010

24 March MOPEC003/4 Fuchsberger et al MOPEC014 White et al

25 30/3/ :15 injected again 12:38 : At 3.5 TeV

26 Soon after the first Collisions

27 A very good 48 hour period! 27

28 IP1&5 lumi vs squeeze Raw (online) lumi plots on 10 apr 2010, during the squeeze to 2m in IP1 and IP5 Factor gained (raw numbers): ~4.5 in Pt5 (after min scan) ~4 in Pt1 Not corrected for lumi decay over the ~5h of squeeze and mini scans atlas

29 LHC Design Bunch Intensity: Thursday Higher intensity Over-injection working well Over-injected 1.1E11, with collimators at nominal 4.5 sigma settings. Emittance at 1E11: 2.5 um H, 2,3 um V. 29

30 Qualification: Off-momentum collimation Loss map for off-momentum error. All OK. See expected low leakage to experimental IR's. OK for stable beams from coll. IR1 IR2 factor 10,000 IR5 IR8

31 Transverse Damper: Damping Beam Excitations Crucial device to keep emittance growth under control! Wolfgang Hoefle et al OFF ON Transverse Damper will stabilize against the Hump 31

32 Collisions with design current at 450GeV

33 Second fill with better lifetime conditions for B1 after RF phase loop adjustment. Stable beams at design current per bunch at 450GeV

34 Closing Collimators During Ramp R. Assmann LHC status 8/6/2010

35 Pushing Number of 2e10 Bunches 2 x 2e10 4 x 2e10 6 x 2e10 per beam 48 hours Allowed doubling the integrated luminosity for 2010 within 48 hours! LHC status 8/6/2010

36 LHC status - week 20&21 13 bunches: 3x10 29!!

37 Recent progress/changes Until 9 June, machine time shared between physics and machine studies. Physics with ~2x10 10 protons/bunch Machine studies to develop 1x10 11 protons per bunch Beam Stored energy is the metre stick: (Machine Protection) Lost particles must end up on collimator or dump Following discussions with the 4 spokespersons and the physics coordinator, a decision was unanimously made on 9 June to concentrate on Machine studies to develop 1x10 11 protons per bunch until it was operational. This meant postponing physics data taking for around 3 weeks. (Minutes LMC 9 th June) 2

38 Getting to Stable beams at 1.1x Instabilities in Collision at 3.5TeV/beam longitudinal emittance control In the SPS During the ramp in the LHC Transverse damper working Collimators set up Injection set up for new high intensity Beam dump set up for higher intensity Started physics data taking under these conditions on Saturday 26 th June (almost a week ahead of estimates)

39 Ramps for Operations set up for protons/bunch

40 26 th June: 5x10 29 with 3 bunches/beam; /b

41 6-8x10 29 cm -2 s -1 with 3 bunches per beam;10 11 /b 29 th June, new record

42 2 nd July: Colliding 6 bunches per beam; /b

43 New Record Lumi > 1e30 cm-2 s-1 LHC status 8/6/2010

44 Beam Lifetime Collisions ALICE LHC status 8/6/2010

45 Beam Intensity Losses LHC status 8/6/2010

46 Tune: Coherent Excitation LHC status 8/6/2010

47 Better but not perfect stability Intensity Luminosity Tuning LHC status 8/6/2010

48 Integrated Luminosity on 7th July

49 Latest News from this morning S. Myers QUB March 11,

50 Summary of Milestones thus far 30 March: first collisions at 3.5TeV/beam 19 April: order of magnitude increase in luminosity doubling the number of particles/bunch β * from 11 to 2m (4b/beam) L ~2x1028. Beam lifetimes of ~1000 hours 22 May another order of magnitude: 13 bunches in each beam (L~ 3x10 29 ) 26 May: Design intensity bunches were brought into collision at 3.5TeV/beam. 2 nd July peak luminosity of cm -2 s -1.

51 Presently From experience so far No fundamental issue for 1e30 luminosity Further equalize beam parameters (emittance, intensity, ) while delivering luminosity. Try to get nominal beam and bunch parameters, including variations. As stability is improved, push up again on luminosity In addition: Cross calibrate emittance measurement devices. Push transverse damper into full operation in collision, however, possibly needs noise reduction. Aim is for before the end of 2010 which is needed for an integrated luminosity of 1fb-1 before end of 2011 LHC status 8/6/2010

52 Peak lumi (in STABLE BEAMS) 1e32!! (modulo some possible luminometers down time...) Fills ~70 days

53 Acknowledgements The work summarized here is the result of work carried out by hundreds if not thousands of scientists, engineers and technicians both employed by CERN and very importantly by the many institutes which collaborate with CERN. It is a great personal pleasure to acknowledge the incredible contributions and dedication of such a wonderful team. 53

54 Thank you for your attention

55 MOPEB042 Bertinelli et al. Clamped and shunted