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New Pbar Cogging in the Tevatron

New cogging for ramp Trying new cogging between pbar injections. New Pbar Cogging in the Tevatron. Ron Moore Fermilab – Tevatron Dept. Pbar Cogging. Use RF system to slip pbars around longitudinally relative to protons Change driving frequency of pbar cavities by ≈10 Hz

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New Pbar Cogging in the Tevatron

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  1. New cogging for ramp Trying new cogging between pbar injections New Pbar Cogging in the Tevatron Ron Moore Fermilab – Tevatron Dept.

  2. Pbar Cogging • Use RF system to slip pbars around longitudinally relative to protons • Change driving frequency of pbar cavities by ≈10 Hz • Pbars injected (4 bunches at a time) into the gaps between proton trains • After 3rd & 6th transfers, cog pbars 84 buckets to clear gaps for next series R. Moore - FNAL

  3. New Pbar Cogging for Acceleration • Pbars are in the abort gap up the ramp • Quench F4 if abort pulled before final cog at flattop • Why suffer needless quenches? • Can we cog pbars out of the gap without introducing problems? • Yuri Alexahin studied beam-beam effects vs cogging position and suggested cogging ≈63 buckets before ramp • +2 buckets with respect to collision cogging • Final cogging still done after reaching flattop • We implemented it for store 5174 R. Moore - FNAL

  4. Bunches ≈380 ns after abort collision cogging: VQCOG3 = 67.96 Gap @ A0 opening up R. Moore - FNAL

  5. Bunches ≈380 ns after abort old pbar cogging on ramp: VQCOG3 = +7 Pbars in gap as kickers ramp up R. Moore - FNAL

  6. Beam-Beam Resonance Strengths vs Cogging at Injection Yuri Alexahin 5Qx Nominal values @ injection ncog=61 (before change) Collision cogging: ncog=0 ncog=-2 is the best for 7Qy ncog=10 is good for 5Qx while not bad for 7Qy: may be used with tunes shifted upwards Now implemented 7Qy ncog RDTs (Resonance Driving Terms) calculated for 3 amplitude

  7. Shot 5174: Last Pbar Injection → Flattop No problems after cogging and up ramp! R. Moore - FNAL

  8. New Cogging during Pbar Injection • During previous study, noticed minima in LOSTP during cogging • Better proton lifetime at those cogging positions? • Try cogging pbars to different location between pbar transfers • Based on next plot, tried +10 buckets on shot 5194 • Manually cogged after the 3rd and 6th pbar injections and cogged back before the subsequent transfers (~1 min at new cogging) • Look (qualitatively) at proton bunch lifetimes – kinks in intensities… • Yuri says +9 buckets should be better…lower 7Qy resonance strength • Also noted lifetime changes after the new cog for the ramp… R. Moore - FNAL

  9. LOSTP vs VQCOG3 (after 3rd pbar injection shot 5174) Try +10 buckets as test Better cog positions between pbar injections? R. Moore - FNAL

  10. P21-P24 New cog before ramp Test cog Effect of cogging on pbar FBI R. Moore - FNAL

  11. P9-P12 R. Moore - FNAL

  12. P29-P32 (after 3rd pbar xfer - 5194) R. Moore - FNAL

  13. P25-P28 New cog before ramp R. Moore - FNAL

  14. Summary • New pbar cogging for the ramp implemented on shot 5174 • Should clear abort gap enough to prevent F4 quenches on an abort • May adjust by 2 buckets and when cogging is done • Investigating new cogging positions between pbar injections for improved proton lifetime • Only tried once, but comfortable with procedure, shows some promise • Some effect on intensity instrumentation • Doing manually now, need help from controls group to automate R. Moore - FNAL

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