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LHC beam operation past , present, future

Recap of LHC beam operation milestones from 2011 to 2012, including current status, challenges faced, and future strategies for optimal performance. Covers key achievements, improvements, and areas of focus for efficient commissioning and operation at the Large Hadron Collider.

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LHC beam operation past , present, future

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  1. LHC beam operationpast, present, future Mike Lamontfor the LHC team

  2. 2011 – recap 75 ns 50 ns Squeeze further Increase number of bunches Increase bunch intensity Scrubbing Reduce beam size from injectors Initial commissioning LHC status

  3. Starting out • Efficient commissioningleading into 75 ns operation • Intermediate energy run • Scrubbing rocky but successful • Dynamic effects: synchrotron radiation, e-cloud  Scrubbing  reduction of the LHC pressure Decision: go with 50 ns LHC status

  4. Number of bunches++ • End April: “fabulous performance” • A little bit of caution – extended period at 1092 bunches • Pushing 1.3e11 ppb but high beam intensity issues starting to show 1033 • Blow-up of some bunches at injection • E-cloud solenoids, triplet vacuum, beam screen cooling • 108 b injection sort of OK, worry about scraping in the SPS • Injection kicker heating, vacuum kicking off in IR8 • RF arc detectors – false dumps • Abort gap population • SEUs starting to show • Collimator heating LHC status

  5. LHC machine breaks 3 new world records at 10h41 Sunday 29 May: 2 x 1092 bunches colliding, luminosity above 1.2 x 10^33, and a beam energy of 73 MJ. LHC status

  6. Looking towards 1380 bunches • Strong emittance blow-up at injection • Chromaticity stability, persistent currentdecay compensation • Eventually suppressed by octupoles at 450 GeV • Bunch length control in ramp • Satellite collisions tested • RF versus intensity versus trips – worrying about couplers – dump on cavity trip deployed • Vacuum at 2&8 - instabilities • Instrumentation issues • UFO storms • High losses at collimators • 1 SEU dump per day • Trim quad circuits tripping during squeeze 15thJune: 1 fb-1 LHC status

  7. Summer - now what do we do? • July: starting to look encouraging… • August: getting so worried about SEUs we had a brainstorming • and a mini-Chamonix • Decision to push: • beam from the injectors • squeeze LHC status

  8. Beam from injectors Excellent performance – years in the preparation • Best in 2011 with 50 ns: • ~1.45 x 1011 ppb • ~2.3 microns into collision • Design with 25 ns: • 1.15 x 1011 ppb • Normalized emittance 3.75 microns LHC status

  9. IR1 and IR5 aperture at 3.5 TeV 2011’s “platinum mine” We got 4-6 sigmas more than the expected 14 sigma Triplet aperture compatible with a well-aligned machine, a well centred orbit and a ~ design mechanical aperture (small tolerance) ~3 cm ~600 m Stefano Redaelli LHC status

  10. Squeeze • Beta* = 1 m – big success – 3.3e33 cm-2s-1 • Pushing bunch intensities to 1.35e11 • Collimator interlocks, PADs/MADs, injection quality, vacuum, collimator heating, Alice background, b2 instability, RF de-bunching, tune feedback in squeeze LHC status

  11. Impressive final run in MirkoPojer LHC status

  12. Very positive ending Ion man LHC status

  13. 2011 • Another remarkable year • It was nearly always a battle… • Remarkably no real show stoppers • Successfully took on: • Total intensity • Bunch spacing • Bunch intensity • Emittance • Beta* & aperture LHC status

  14. Of note • Operational robustness • Precycle, injection, 450 GeV, ramp & squeeze & collisions • Machine protection • Unpinned by superb performance of machine protection and associated systems • Rigorous machine protection follow-up, qualification and monitoring (Post Mortem analysis, MPP, rMPP) • Routine collimation of 110 MJ LHC beams without a single quench from stored beams. LHC status

  15. Operation efficiency • Overall efficiency • Pretty good considering that this is the LHC • Overall time in stable beams 34% • Premature dumps • 50% of all STABLE BEAMS fills lasted less than 3 hours 34% LHC status

  16. Radiation to electronics (R2E) • xMas-Mitigation crucial: patch, shielding, relocat. • Patches to continue during 2012 • Particular emphasis (analysis) of ‘new’ failures LHC status

  17. Concerted program of investigations, simulations, tests with beam … Tobias Baer LHC status

  18. Vacuum • Unexpected pressure rise (10-6 mbar) observed in LSS2-LSS8 (D1) and close to CMS: bad RF contact (x-rays inspection) interventions done in 2 & 8 & CMS to resolve RF finger issues - shouldn't be a problem in 2012. CMS LSS2 LHC status

  19. TDI – beam screen heating LHC status

  20. 2011 to 2012 • Well organized, productive Xmas technical stop • Lot of R2E related work • Plus consolidation and improvements of many systems • Vacuumconsolidation to address successfully diagnosed causes of instabilities in 2011 • Injection collimators issues diagnosed and understood - spare in preparation - fingers crossed in the meantime • Cool-down of machine exactly on schedule - cryogenics demonstrating full mastery… • Very smooth hardware commissioning including careful quench-less commissioning of main circuits to 4 TeV • Machine checkout proceeding well - good for beam next Tuesday afternoon LHC status

  21. 2012 strategy 4 TeV β*=0.6m→0.7m→0.9m 50 ns ∫Ldt = 5 fb-1 in June? Dumps=30-50 ∫Ldt = 15-19 fb-1 Pile-Up=26-35 LHCb ∫Ldt=1.5 fb-1 Lpeak=5-6.8 1033 cm-2s-1 TCP gap=2.2mm IP1 β*=500m SPS ε= 2 μm SPS Np= 1.6 1011 p-Pb: 3.5 TeV or 4 TeV • ∫Ldt = 15- 23 nb-1 β*=(0.6,0.6,0.6,3)m LHC status Rogelio Tomas

  22. Collimator settings 2012 Collimation hierarchy has to be respected in order to achieve satisfactory protection and cleaning 2012: tight settings LHC status

  23. How tight? Norway Iberian peninsula Intermediate settings (2011): ~3.1 mm gap atprimary collimator Tight settings: ~2.2 mm gap atprimary collimator LHC status

  24. 2012 run configuration • Energy – 4 TeV • Low number of quenches (as in 2011) assumed • Bunch spacing - 50 ns • Collimator settings – tight • As discussed – NB not yet proven operationally • Atlas and CMS beta* - 60 cm • with 70 cm and 90 cm as fallbacks • Alice and LHCb beta* - 3 m • Natural satellites versus main bunches in Alice LHC status

  25. Bunch spacing Performance from injectors LHC status

  26. 2012 LHC schedule Q1/Q2 1 2 3 4 LHC status

  27. 2012 LHC schedule Q3/Q4 6 5 High beta* runs for ALFA and TOTEM Van der Meer scans LHC status

  28. 2012 - breakdown ~150 days LHC status

  29. 50 ns performance estimate 4 TeV, 50 ns, 1380 bunches, 1.6e11, 2.5 microns150 days of proton physics (assuming similar efficiencies to 2011) LHC status

  30. 25 ns performance estimate 4 TeV, 25ns, 1380 bunches, 1.6e11, 2.5 microns140 days of proton physics (extra scrubbing required) Conclusion: 25 ns not competitive with 50 ns LHC status

  31. LHC status

  32. Conclusions • Good performance in 2011 from working on all available parameters • Very definitely exploring the effects of high intensity beams • SEUs, beam induced heating, vacuum instabilities… • Operational efficiency suffering as a result • Main gain in 2012 is use of tight collimator settings and reduced beta* • 5 to 6 x 1033 cm-2s-1 and 15 fb-1 should be possible • Hope for improved operational efficiency • R2E mitigation measures • but partially countered by increased peak performance • Another long, interesting year in prospect… LHC status

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