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Anti-Proton Cooling

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

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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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