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LHC Status & Plans

LHC Status & Plans. V. Kain, LHC Operations Input from: J. Wenninger, F. Zimmermann, R. Assmann, S. Myers, J.P. Koutchouk, L. Evans, A. Verwej, H. Burkhardt.... SLAC SLUO workshop 16 th – 17 th of July. Outline. Beam Commissioning September 19 th Incident The cause, the problem...a cure?

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LHC Status & Plans

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  1. LHC Status & Plans V. Kain, LHC Operations Input from: J. Wenninger, F. Zimmermann, R. Assmann, S. Myers, J.P. Koutchouk, L. Evans, A. Verwej, H. Burkhardt.... SLAC SLUO workshop 16th – 17th of July

  2. Outline Beam Commissioning September 19th Incident The cause, the problem...a cure? 2009/10 LHC run ...And beyond – LHC Upgrade Summary

  3. First beam around the LHC All sectors at nominal temperature LHC Cool-down Cool-down time to 1.9 K ~ 4-6 weeks/sector [sector = 1/8 LHC]

  4. LHC Hardware Commissioning 11’122 test steps February to September 2008 • (Re-)commissioning of the magnets & circuits (power converter, quench protection, interlocking..) following predefined test steps. • 1’700 circuits, 10’000 magnets • LHC was commissioned to 5.5 TeV (5 TeV target for physics in 2008). • Magnet re-training required above ~6 TeV. • Commissioning of other equipment (kickers, instrumentation, RF,…)

  5. Injection Tests 22nd – 24th of August 8th – 10th of August 5th – 7th of September Evening of August 8th 2008: First beam in the LHC after ~25 years of design and construction. August – September 2008 • Injection tests up to 4 adjacent sectors • Almost all HW systems involved • Essential checks for: • Control system • Beam Instrumentation • Optics (magnetic model) and aperture

  6. September 10th

  7. Beam Threading Beam 2 threading BPM availability ~ 99% • Threading by sector: • One beam at a time AND one beam per hour • Collimators used to intercept beam (1 bunch, 2 × 109 protons per bunch, 2 % of nominal bunch) • Beam through sector (1/8 of ring), correct trajectory, move out collimators, carry on.

  8. Courtesy of ATLAS ATLAS & CMS “events” Courtesy of CMS • Beam-on-collimator events, synchronized to beam timing

  9. Beam Commissioning Progress • September 10th • 10:30: Beam 1 around the ring (in ~ 1 hour). Beam makes ~ 3 turns • 15:00: Beam 2 around the ring. Beam makes 3-4 turn • 22:00: Beam 2 circulates for 100s of turns • September 11th • Late evening beam 2 captured by RF. • First emergency dump correctly executed. • September 12th • All basic instrumentation operational: BPMs, BLMs, Tune, BCTs,... • Good beam lifetime (> 1 hour) • Beta-beating measured

  10. Magnetic model & beta-beating Beta-beat tolerance : 20% Dominant source of beating identified as trim quadrupole inversion between beam1 & beam2. • Horizontal beating ≤ 30% • Vertical beating up to 90-100% • A sophisticated magnetic model (FIDEL) was developed to predict transfer functions and field errors for all magnets, backed by measurements and integrated into the control system for online corrections.

  11. September 19th incident

  12. Event sequence on 19th of September • Last commissioning step on main dipole circuit in Sector 34: ramp to 9.3 kA (5.5 TeV) • At 8.7 kA an electrical fault developed in the dipole bus bar in the interconnect between Q24.R34 and the neighbouring dipole • Later correlated to a resistance of that splice in the interconnect of ~ 220 nW (0.35 nW nominally) • An electrical arc developed which punctured the He enclosure • Secondary arcs developed along the circuit • Around 400 MJ out of the 600 MJ stored in the circuit were dissipated into the coldmass and in electrical arcs. • Tons of He were released into the insulation vacuum • Pressure wave along the magnets in the insulation vacuum → collateral damage

  13. Interconnection Vac. chamber Dipole busbar

  14. After the incident... Dipole bus bar

  15. Collateral damage – pressure wave • He-pressure wave travels along magnet inside insulation vacuum up to vacuum barriers (every 2 cells) • Self actuating relief valves could not handle pressure • Designed for 2 kg He/s: incident ~ 20 kg He/s • Large forces exerted on vacuum barriers • Designed for 1.5 bar: incident ~ 8 bar • Several quadrupoles displaced by ~ 50 cm • Connection to cryo-line damaged • Beam vacuum atmospheric pressure

  16. Collateral damage - beam vacuum Clean surface Covered with MLI flakes ~ 60 % of all chambers Covered with soot. ~ 20 % of all chambers Beam vacuum affected over entire length of arc: 2.7 km

  17. LHC Repair

  18. The Cause, the problem...a cure?

  19. Incident cause: poor quality joint • Cryogenic measurements indicate local resistance of superconducting cable joint of ~ 220 nOhm in cell where incident occured. • Simulation of fatal ramp: “thermal runaway at 8700 A” • 1 V detection threshold of “OLD” quench protection system (QPS) not adequate • → 0.3 mV is required to protect busbars → new QPS system

  20. Busbar quench: current through Cu stabilizer

  21. Bad connection in Cu stabilizer→ New QPS does not protect

  22. Bad Cu stabilizer: bus bar quench • Has to be measured at warm.

  23. Measurement at cold: 1.9 K Cold 1.9K Goal for next run: beam energy 4 TeV – 5 TeV Splices above inadequate resistance have to be fixed

  24. Measurement at300 K (80 K) Copper stabilizers... “simulations are only as good as their input conditions...”

  25. Measurement status & strategy NEW QPS TO PROTECT! DANGEROUS IN CASE OF QUENCH • SC joint measurements: calorimetry (down 40 nOhm), high precision voltage (down to 1 nOhm) measurements,... • 3 sectors still to be tested (S34, S23, S45): so far: • two “bad” internal joints found (50 nOhm, 100 nOhm) • Cu stabilizers: • 3 sectors still to be tested (S 23, S 78, S 81): so far: • MB: 10 joints repaired > 35 mOhm • MQ: 10 joints repaired > 80 mOhm • Strategy: • Measure remaining sectors • Determine which splices need to be repaired as a function of safe current • Discuss safe operating energy vs. start-date with beam

  26. LHC run 2009/10 - Plans

  27. Current Planning • Machine fully hardware-tested end of October. • First beam end of October. • ...followed by a long LHC run until November 2010 with a short break around Christmas/New Year. • Target energy 4 – 5 TeV Cool-Down Low cur. powering High cur. powering

  28. Luminosity Goals No crossing angle Present 4-stage collimation system limits intensity to ~ 10 % of nominal. Operational goals 2009/10 End of 2010: short Pb ion run foreseen

  29. sLHC – Luminosity upgrade ...And beyond – LHC upgrade

  30. Upgrade for Nominal - Collimation • Coming either • 2010/11 or 2013/14 • cryo-collimators • low impedance collimators → HiRadMat • in-built BPMs Issue: loss of off-momentum particles in the dispersion suppressor right downstream of collimation zones.

  31. LHC Luminosity Upgrade Limitations: Nb, en injector chain nb electron cloud effect F beam separation schemes b* insertion sLHC: Phase I sLHC: Phase II Luminosity upgrade → sLHC

  32. Plans... Phase I: 2014 Phase II: 2018

  33. Phase I and Phase II Still open questions • Phase I - 2014 • New NbTi larger apterure triplets, new quadrupole absorbers (TAS), new separation dipoles → b* = 25 cm • Linac4 → ultimate intensity 1.7 × 1011 p+ per bunch • Luminosity: 3 × 1034 cm-2s-1 • Phase II - 2018: • Two new injectors: SPL and PS2 → 2x ultimate beam brightness (Nb/e) • New triplets? Nb3Sn? More robust, larger aperture → b* = 15 cm • New separation schemes? Other compensatory measures? • Luminosity: 1035 cm-2s-1

  34. Phase II: new separation scheme required for nominal crossing angle (“9.5 σ”), only modest luminosity gain from reduced β*, if not complemented by other measures Crossing angle reduces beam-beam tune shift but also luminosity. Geometric factor Piwinski angle

  35. Beam separation schemes/ Compensatory measures: possibilities SPS wire Beam-beam compensation 1.7-2.3 × 1011 per bunch, 25 ns Crab crossing • Low emittance: 1- 2mm • Draw back: limited by beam-beam tune shift and IBS • Work against lumi-decrease from geometric overlap reduction: different possibilities • Long-range beam-beam compensation • Early separation: dipole magnets in experiment • Plus possible crab cavities • Full crab crossing with dedicated crab cavities • “Large Piwinski angle” – at beam-beam limit: larger Piwinski angle (and/or larger emittance) increases luminosity: 50 ns, 4.9 × 1011 p+ per bunch

  36. Contact Names - Upgrade • http://project-slhc.web.cern.ch/project-slhc/contacts/ • sLHC project leader: L. Evans • Linac4: M. Vretenar, A. Lombardi • SPL: R. Garoby, A. Lombardi • PS2: M. Benedikt, Y. Papaphilippou • SPS upgrade: E. Shaposhnikova • IR upgrade (phase I): R. Ostojic, S. Fartoukh: http://slhc-irp1.web.cern.ch/SLHC-IRP1/ • EuCARD Coordinator: J.-P. Koutchouk https://eucard.web.cern.ch/EuCARD/about/ • Crab cavities: J. Tuckmantel, F. Zimmermann • Collimators: R. Assmann • High field magnets: L. Rossi • .... • Other things: • Machine protection, operational issues, software,...: J. Wenninger, R. Schmidt, V. Kain

  37. Summary • With beam the LHC is a wonderful machine. • All key systems were operational • Remarkable performance of the beam instrumentation • The incident of the 19th of September was most probably due to the poor quality of a bus-bar joint. • → Quench protection system upgrade • → Improvement of the pressure relief system • → Measurement campaign for all splices and stabilizers: systematic problem • Repair and further measurements are well under way • We will start-up in autumn this year. The goal is to run until autumn 2010. • Upgrade: luminosity upgrade in several stages. Different work packages have been defined. • Collimators need upgrade to go to nominal intensity • The first upgrade phase is planned for 2014

  38. Reserve slides

  39. Bad surprise...voids in joints Voids are present in most of the joints. Solder (SnAg) flows out when soldering in situ.

  40. Splice and Stabilizer Measurements (Status June 5)

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