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Tevatron Performance and Perspectives

Tevatron Performance and Perspectives. Keith Gollwitzer Fermi National Accelerator Laboratory. Fermilab. The Tevatron. Superconducting Synchrotron Operates at 4K Radius of 1 km; revolution time ~21 μ s Proton – Antiproton Collisions 36 bunches in each beam 3 trains of 12 bunches

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Tevatron Performance and Perspectives

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  1. Tevatron Performance and Perspectives Keith Gollwitzer Fermi National Accelerator Laboratory

  2. Fermilab Gollwitzer - HCP2006

  3. The Tevatron • Superconducting Synchrotron • Operates at 4K • Radius of 1 km; revolution time ~21 μs • Proton – Antiproton Collisions • 36 bunches in each beam • 3 trains of 12 bunches • 396 ns spacing • Bunch length of ~19 ns • Each beam is 980 GeV • Each beam on helical orbits except at the detectors interaction points Gollwitzer - HCP2006

  4. Protons Gollwitzer - HCP2006

  5. Antiprotons • Created from 120 GeV Protons from Main Injector • Production Target is nickel alloy followed by a pulsed lithium collection lens • Collected using three rings at 8 GeV • Debuncher • Accumulator • Recycler • Cooling systems reduce the phase space and increase beam density • Main Injector is used to accelerate pbars to 150 GeV for injection into the Tevatron Gollwitzer - HCP2006

  6. Luminosity • The major contributors to determining the luminosity are: • Number of particles in each bunch (N) • The transverse emittances of the beams (ε) • Transverse beam optics at the interaction point (β*) Gollwitzer - HCP2006

  7. 6dB/div Energy Antiproton Stacking - Past Only Accumulator Stochastic cooling limited the number of pbars used for physics The stacking rate slows as the core grows Stacking cycle time would go from 2.2s to > 6.0s when going from an empty Accumulator to 1.5e12 pbars in roughly 1 day. Gollwitzer - HCP2006

  8. Antiproton Stacking - Present • Accumulator off-loads pbars to Recycler • When the Accumulator has ~0.6e12 pbars - Transfer • Keeps stack cycle time small: ≤ 2.6s • Recycler (prior to Oct 2005) • Together with Accumulator provide more pbars • Recycler - Electron Cooling (since Oct 2005) • First time done with relativistic electron beam • Able to make denser pbar bunches • Routinely have 2-3e12 pbars available for Tevatron • Pbars to Tevatron come only from Recycler Gollwitzer - HCP2006

  9. Recycler Electron Cooling Longitudinal stochastic cooling of 8 GeV antiprotons in the Recycler has been replaced by Electron Cooling Electron beam: 4.34 MeV – 0.5 Amps DC – 200mrad angular spread Max beam current 730 mA Circulated in cooling section In U-Bend mode currents of 1500 mA has been obtained. Gollwitzer - HCP2006

  10. First Electron Cooling 07/15/05 After demonstration, time was spent learning how to control the cooling via electron current and relative beam positions. Was brought into operations in 2.5 months Gollwitzer - HCP2006

  11. Tevatron Optics Change • 28 cm β* + optics correction • Lattice measurements exploited new BPM electronics • Tested at end of stores; implemented in September • Decrease β* β* Measurements by D0 Gollwitzer - HCP2006

  12. 28 cm β* + Recycler-only pbars Initial Luminosities Gollwitzer - HCP2006

  13. More Antiprotons • Increase the Stacking Rate • The Accumulator’s stochastic cooling systems configuration is a balance between the rate and maximum stack size. • With Recycler taking the “storage” role, the Accumulator can focus on stacking rate • More protons on Production Target • Antiproton collection efficiency (aperture of the beam line from the target to the Debuncher) • Speed of the Debuncher and Accumulator Stochastic cooling systems • Accumulator stochastic cooling systems configuration Gollwitzer - HCP2006

  14. Orbits & Protons for Antiproton Production New Beam Position Monitor electronics allowed feedback for orbit control Particles 200m downstream of target (108) November 2005 January 2006 10mm per division Protons on target (1012) 3hour per division Gollwitzer - HCP2006

  15. Stacking Rate Cooling systems configuration Best stacking for 1 hour for each day Average Stacking rate for a week Increase aperture Increase protons on target Gollwitzer - HCP2006

  16. Q. Why not more Protons? • A. Beam-Beam Interactions • Minimize by trying to keep beams as well separated as possible • Electrostatic Separators • Near misses on each side of the collision points • Not the same for leading/trailing train bunches as the middle bunches • Mainly the antiprotons are affected by tune shifts and blowing up the beam emittance Gollwitzer - HCP2006

  17. Pbar horz Pbar tunes decrease by ≈0.01 Pbar horz tune Pbar vert Orbit stabilization ON E11 vert BPM [mm] Pbar vert tune Prot horz Prot vert F17 horz BPM [mm] New BPM electronics help us see this motion! Pbar horz change Pbar vert change Proton vert tune Pbar lifetime [hr] Store 4121 Lumi lifetime [hr] D0 proton halo [Hz] Store 4639 C4Q4 roll [μrad] C4Q4 pitch [μrad] Proton intensity [E9] Tevatron Tune & Orbit Control Reduction of beam halo seen by the experiments Gollwitzer - HCP2006

  18. A Week of Operations 3e12 40 pb-1 2e32 cm-2 s-1 3e12 Recycler Beam Integrated Luminosity Luminosity Accumulator Beam Gollwitzer - HCP2006

  19. Peak Luminosity Gollwitzer - HCP2006

  20. Integrated Luminosity Gollwitzer - HCP2006

  21. Tevatron Complex “Bests” • Initial Luminosity: 1.7e32 cm-2 s-1 (Jan06) • Store Integrated Luminosity: 6.7 pb-1 (Feb06) • Protons to collisions: 10.0e12 (Aug03) • Antiprotons to collisions: 2.5e12 (Jan06) • Antiprotons in Accumulator: 2.5e12 (Dec03) • Antiprotons in Recycler: 4.4e12 (Feb06 ) • Accumulator Stacking Rate: 0.2e12/hr (Feb06) Gollwitzer - HCP2006

  22. 5 cm Improve on “Bests” • Mostly more Antiprotons • Stack faster • More into Recycler • More into Tevatron • Tevatron • New helical orbits • More separators Gollwitzer - HCP2006

  23. Increase in protons on target Stacking Improvements • Increase Accumulator stacking rate from 0.2e12/hr to 0.2.5e12/hr by the end of this year Increase Lithium Lens strength Gollwitzer - HCP2006

  24. Stacking Improvements • Increase Accumulator stacking rate to 0.3e12/hr over the next year • Aperture improvements • Largest gain is this • Target to Debuncher • Secondaries • Stochastic cooling • Speed • configuration Gollwitzer - HCP2006

  25. Recycler • Still learning how to use the electron cooling system optimally • Every time new record number of antiprotons has led to learning how to optimize the operation of the Recycler • Should be able to store ≥ 6e12 antiprotons • Note that initial luminosity record started with 3.3e12 antiprotons in the Recycler Gollwitzer - HCP2006

  26. Other Items • Continue to improve efficiencies • Transfer between machines • Ramping • Decrease stacking downtime • Shorten the amount of time it takes to transfer antiprotons from the Accumulator to the Recycler Gollwitzer - HCP2006

  27. Projections 1mA = 1e10 Antiprotons in Accumulator Gollwitzer - HCP2006

  28. Conclusions • The Fermilab Tevatron complex has delivered ~1.5 fb-1 to each experiment • Looking forward to hearing CDF and D0 results from these data sets this week • 8 fb-1 should be achieved in 2009 • Dependent upon Accumulator stacking rate • Optimization of the Recycler operations with electron cooling will continue Gollwitzer - HCP2006

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