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Successful compensation of Beam-Beam effects on protons with Tevatron Electron Lens

Successful compensation of Beam-Beam effects on protons with Tevatron Electron Lens. Vsevolod Kamerdzhiev (AD/APD) for Beam-Beam Compensation Team V.Shiltsev, V.Kamerdzhiev, G.Kuznetsov, X.L.Zhang Yu.Alexahin, H.Pfeffer, G.Saewert, V.Scarpine All Experimenters Meeting Jan 8, 2007.

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Successful compensation of Beam-Beam effects on protons with Tevatron Electron Lens

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  1. Successful compensation of Beam-Beam effects on protons with Tevatron Electron Lens Vsevolod Kamerdzhiev (AD/APD) for Beam-Beam Compensation Team V.Shiltsev, V.Kamerdzhiev, G.Kuznetsov, X.L.Zhang Yu.Alexahin, H.Pfeffer, G.Saewert, V.Scarpine All Experimenters Meeting Jan 8, 2007

  2. 2003: pbar blowup suppressed by TEL-1 Store #2540 May 13, 2003 Emittance evolution at the start of the store A9 4.1  mm mrad/hr A21 2.2  mm mrad/hr A33 1  mm mrad/hr TEL-1 acts on it BBComp experiments have been performed in few stores, TEL-1 was needed to clean abort gaps. All Experimenter's Meeting - Dec 8, 2007

  3. Important changes since then • New electron guns developed with wider and more optimized electron beam profiles * • Orbit stabilization in Tevatron, better beam diagnostics (bunch-by-bunch 1.7GHz Schottky) • Much better understanding of beam-beam effects • TEL-2 built and installed (2006 shutdown) that can be used for studies ** (TEL-1 still works 24/7 in abort gaps) • Ability to use & tune up TEL-2 parasitically in stores at low e-current on a single bunch • Beam-beam compensation efforts switched from antiprotons to protons *** All Experimenter's Meeting - Dec 8, 2007

  4. Electron guns developed for TELs Initial (2001) Used for Pbar Compensation (2003) Used now (2005) E-beam is strongly magnetzed in 2-40 kG magnetic field Profile shape inthe interaction region is the same  All Experimenter's Meeting - Dec 8, 2007

  5. TEL-2 in the tunnel (A0) All Experimenter's Meeting - Dec 8, 2007

  6. What to compensate? protons or pbars? Protons Antiprotons At present, beam-beam effects are stronger on protons, accounting for some 10-15% loss of the integrated luminosity. Proton loss rates vary greatly from bunch to bunch. The Tevatron Electron Lens #2 is aligned on proton beam. All Experimenter's Meeting - Dec 8, 2007

  7. TEL-2 e-beam aligned and timed on protons in space in time TEL P12 P9 P10 P11 A24 Transverse e-p alignment is very important for minimization of noise effects and optimization of positive effects due to e-beam. Timing is important to keep protons on flat top of e-pulse – to minimize noise and maximize tune shift. All Experimenter's Meeting - Dec 8, 2007

  8. TEL-2 on P12: 1st hour of store #5119 TEL-2 current Bunch P12 – TEL-2 acts on it Bunch P36 – not affected by TEL-2 All Experimenter's Meeting - Dec 8, 2007

  9. TEL-2 improves proton bunch lifetime All Experimenter's Meeting - Dec 8, 2007

  10. The improvement is reproducible Store #5123 Store #5119 Store #5127 All Experimenter's Meeting - Dec 8, 2007

  11. Why does that happen? Bunches are not equal! TEL-2 moves Qv up Bunch P12 has systematically the lowest vertical tune that reduces its lifetime (too close to 7/12 resonance). TEL-2 raises the tune by 0.001-0.002. All Experimenter's Meeting - Dec 8, 2007

  12. Summary • Tevatron Electron Lens-2 was installed during 2006 shutdown and commissioned as i) TEL-1 backup for abort gap cleaning ii) as vertical beam-beam tune shift compensator ΔQv~.002 • In a series of stores, TEL-2 acted on a single proton bunch and DOUBLED its lifetime • BBCompensation helps for ~10 hrs in store • Next attempts: (fix HV modulator), use TEL-2 during scraping, on many bunches in stores. All Experimenter's Meeting - Dec 8, 2007

  13. Finally – many thanks to: • Bosses for support • Many colleagues for advice • Cryo, Mech. Support and EE Support for care • TD for fixing our magnets • Brian and Salah for patience and cooperation All Experimenter's Meeting - Dec 8, 2007

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