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Tevatron Operations Post-Shutdown: Maintenance, Challenges, and Luminosity Improvements

Following the Tevatron's shutdown, operations resumed with extensive maintenance and unexpected component replacements. Key activities included warming vacuum houses and adjusting beam configurations to manage proton losses during the new helix transition. Despite some improvements, further adjustments led to reverting to an older helix scheme due to high pbar losses. Luminosity saw incremental gains with adjustments like alpha-bumps, but challenges remain in achieving optimal intensities and mitigating losses. Overall, Tevatron aims for greater reliability and higher integrated luminosity as operations continue.

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Tevatron Operations Post-Shutdown: Maintenance, Challenges, and Luminosity Improvements

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  1. Tevatron Operations Since the Shutdown Ron Moore Fermilab – Tevatron Dept.

  2. Shutdown/Startup Work • No big upgrades, but lots of maintenance • Warmed up 4 houses for vacuum work • Found/replaced unexpectedly a few (electrically) bad components • Unroll ~60 dipoles, lattice quads (including D16-1 ≈20 mrad) • Move CDF and D0 triplets to move IP and lower corrector currents • Adjusted CDF again after start-up since IP far off (?) • Start up with new helical orbits (horz & vert collision, vert injection) • Goal was to eliminate proton loss during helix transition in squeeze • Had to revert after high pbar loss in new transition R. Moore - FNAL

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  5. As good as ever… R. Moore - FNAL

  6. Losses during Squeeze • Proton loss is driven by beam-beam effects • New helix more complicated that initially thought • Flip horz collision helix in short arc to eliminate B17H separator polarity change • Also need vert collision helix flip to allow initiating collisions in usual way • Flip vert injection helix to prevent C17V separator polarity change in squeeze • Lost ~1/3 pbars during new helix transition in squeeze of 1st 36x36 store • Phase changes of helix allowed horz and vert separation minima to coincide • Nearly head-on collisions in many places around the ring • Some improvements made, but not good enough  revert to old helix scheme • Made improvements after tuning-up and making orbit bumps to reduce losses at CDF and D0 R. Moore - FNAL

  7. Shot 5802 – (Smaller) Proton Loss during Squeeze Low-β LBSEQ Proton Intensity [109] Proton Loss @ Helix Transition Pbar Intensity [109] LBSEQ 14 D11 BLM [Rad/s] Loss Spikes CDF BLM [Rad/s] R. Moore - FNAL

  8. Improved Proton Efficiency in Squeeze R. Moore - FNAL

  9. HEP • Luminosity ramping up with beam intensities • D0 luminosity lower than expected • Made 3% improvement with alpha-bumps (horz and vert β* offset longitudinally) • Still not understood completely R. Moore - FNAL

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  11. Lifetimes in HEP • Pbar lifetime is improved – almost entirely luminous • Proton lifetime suffering from small pbar emittances • Pbars 3-4 times smaller than protons • Greater fraction of proton bunch sees strongest beam-beam force • Highest head-on tune shifts for protons > 0.024 • Trying to blow-up pbars last few stores (missteering at injection) R. Moore - FNAL

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  13. Proton Burn Rates – Store 5802 Mary Convery Measured burn rate Non-luminous burn rate Non-luminous losses dominate early in HEP Burn rate from luminosity R. Moore - FNAL

  14. Jerry Annala R. Moore - FNAL

  15. 5 store running average R. Moore - FNAL

  16. Summary • Post-shutdown start-up longer than desired • Adjust CDF quads (again) and revert to old helix • Beam losses at injection, ramp, squeeze as good or better • Luminosity ramping up with beam intensities • Proton lifetime early in HEP is an issue • Exacerbated by small pbar transverse emittances • Want higher intensities to push integrated luminosity • 15-20% more protons and pbars to return to pre-shutdown • Get back to > 40 pb-1 per week reliably R. Moore - FNAL

  17. Pbars in the Squeeze R. Moore - FNAL

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