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Optimizing New Pbar Cogging Techniques in Tevatron for Enhanced Proton Acceleration

This report details the implementation of new Pbar cogging techniques at Fermilab's Tevatron, aimed at improving the longitudinal alignment of antiprotons relative to protons during acceleration. By adjusting the RF system to slip pbars around longitudinally and modifying the driving frequency of pbar cavities, we enhance beam stability while minimizing unnecessary quenching. Initial tests have shown promise in improving proton lifetime and reducing beam-beam resonance strengths. Further investigations will focus on optimizing cogging positions between pbar injections for better outcomes.

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Optimizing New Pbar Cogging Techniques in Tevatron for Enhanced Proton Acceleration

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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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