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Anti-Proton Cooling

The Tevatron Operations Review presents an overview of anti-proton cooling techniques led by Paul Derwent. Key methods include stochastic cooling and electron cooling utilized in the Recycler, Debuncher, and Accumulator systems. The emphasis is on reducing emittance and increasing particle density through different frequency bands, achieving improvements in cooling times and phase space dimensions. The review outlines operational experiences, performance measures, and ongoing enhancements to optimize cooling processes critical for efficient anti-proton beam operations.

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Anti-Proton Cooling

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  1. Anti-Proton Cooling Paul Derwent DOE Tevatron Operations Review March 21, 2006

  2. Overview and Goals • Recycler: ~1 day • Stochastic cooling • 0.5-1 GHz & 1-2 GHz momentum • 2-4 GHz transverse • Electron cooling • 0.5 A 4.34 MeV beam • Needs transverse overlap of electron and anti-proton beam • Longitudinal Emittance ~ 54 eV-sec • Transverse Emittance ~ 5 π mm mr • 600e10 • Debuncher: 2 seconds • Stochastic cooling • 4-8 GHz • Liquid He cooled slotted waveguide pickups • Factor of 10 in longitudinal phase space • Factor of 7-10 in both transverse phase space dimensions • ~1.6e8 pbars (~30e10/hr) • Accumulator: ~few hours • Stochastic cooling • 2-4 GHz stacktail, 2-4 & 4-8 GHz core momentum • 4-8 GHz transverse slotted waveguide pickups • Preserve Longitudinal phase space • Increase particle density by factor of 5000 • Factor of 3-5 in both transverse phase space dimensions DOE Tevatron Operations Review - Paul Derwent

  3. Debuncher Cooling • Transverse Cooling: • >300 π mm mr • 1-2e8 per pulse • Power limited (TWT and kickers) • Design*: • 1e8 particles • Cooling time ~0.7 sec • Measure: • ~1e8 • Horizontal: 0.69±0.03 sec • Vertical: 0.74±0.03 sec • Factor of 17 in 2 seconds • Expect factor of 12 for 2e8 (36e10/hr) *J. Marriner,. Fermilab Pbar Note 573, http://www-bdnew.fnal.gov/pbar/documents/pbarnotes/pdf_files/PB573.PDF DOE Tevatron Operations Review - Paul Derwent

  4. Debuncher Cooling • Momentum Cooling: • Design: • Factor of 10 in 2 seconds • Measure: • Cooling time 0.32 seconds • Factor of 13 in 2 seconds • Asymptotic width defined by gain and intensity • Ramp gain down through cycle • Distribution fills the notch • Heating from other particles DOE Tevatron Operations Review - Paul Derwent

  5. Debuncher Cooling Measure for 1e8 particles: Transverse: Factor of 17 in 2 seconds Expect factor of ~12 for 2e8 particles Limited by available power Add notch filters to B3 & B4 - more power for cooling? Optimize gain ramp? Longitudinal: factor of 13 in 2 seconds Limited by asymptotic width, not rate 2 turn notch filters for half cycle? Optimization of mix of transverse and longitudinal (e.g., gate off initially to give transverse a head start?) DOE Tevatron Operations Review - Paul Derwent

  6. Accumulator Cooling • Stacktail: van Der Meer solution: • Constant Flux: • Solution: • Exponential Density Distribution generated by Exponential Gain Distribution • Max Flux = (W2|h|Ed)/(f0p ln(Fmax/Fmin)) • W bandwidth, Fmaxand Fminfrequency range • f0 beam revolution frequency, p beam momentum • |h| phase slip factor • Edcharacteristic gain slope DOE Tevatron Operations Review - Paul Derwent

  7. Accumulator Cooling • Interplay between stacktail and core: • Stop constant flux and accumulate! • Ed changes • 2-4 GHz core momentum • Same bandwidth • Flux goes down • 4-8 GHz core momentum • Higher bandwidth • Sustain flux for longer • Core `back pressure’ will require transfer to Recycler to sustain flux DOE Tevatron Operations Review - Paul Derwent

  8. Core 4-8 GHz Momentum Cooling System Bandwidth • 1 GHz of bandwidth at 7 GHz is ~3x more powerful than 1 GHz of bandwidth at 2.5 GHz • ln(Fmax/Fmin) • By replacing the trunk coaxial cable with optical fiber, the 4-8 GHz system will be 5.7x more powerful than the 2-4 GHz system DOE Tevatron Operations Review - Paul Derwent

  9. Accumulator Cooling • Measurements of bandwidth and slope: • 1.2 GHz • 9.5 MeV • ~30 mA/hour max • Change Ed by moving pickup tank ~8 mm, adjust relative gains and phase • 12 MeV • ~36 mA/hour max • Bandwidth upgrade: 4-6 GHz pickups and kickers • 9 MeV • ~50 mA/hour max • 10 Feb 06: 20.12e10 in one hour • Ed ~ 9.5 MeV • Gain, bandwidth from core 4-8 DOE Tevatron Operations Review - Paul Derwent

  10. Record Hour DOE Tevatron Operations Review - Paul Derwent

  11. Accumulator Cooling 2003 Plan: Implement 4-8 Core momentum cooling In Progress: bandwidth and gain improvements Tank Move option (dependent on input flux) Probably in next year 4-6 GHz bandwidth upgrade (dependent on input flux) When flux requires it DOE Tevatron Operations Review - Paul Derwent

  12. Recycler Cooling • Stochastic cooling: • To prepare injected beam for integration into main stash • Transverse cooling so that e-beam overlaps anti-proton beam • Goal: 15 π -> 10 π in 25 minutes for 25e10 • ~5 π for shots • Electron cooling: • Majority of work in longitudinal space DOE Tevatron Operations Review - Paul Derwent

  13. Recycler Cooling • Operational experience with e-cool • Optimize operational mix between e-cool & stochastic cooling -- learning experience • Best setup of stochastic cooling? • Gain gating: • stash and injected beam separated in time (barrier buckets) with much different characteristics (>300e10 vs 25e10) • Different gain for stash and injected beam? • Change momentum system to transverse • Cool injected beam faster transversely, let e-cool take over? DOE Tevatron Operations Review - Paul Derwent

  14. Anti-proton cooling • Cooling systems effectively handling 20e10/hour • Measurements show can handle 30e10/hour • Burden moving from Accumulator to Recycler! • Working on upgrades (stacktail) and optimization (Debuncher, Recycler) to gain operational margin for >35e10/hour DOE Tevatron Operations Review - Paul Derwent

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