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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. - PowerPoint PPT Presentation
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Successful compensation of Beam-Beam effects on protons
with Tevatron Electron Lens
Vsevolod Kamerdzhiev (AD/APD) forBeam-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
BBC Team All Experimenter's Meeting - Dec 8, 2007 2
2003: pbar blowup suppressed by TEL-1
Store #2540Store #2540
May 13, May 13, 20032003
A33
1 mm mrad/hr
TEL-1 acts on it
A21
2.2 mm mrad/hr
A9
4.1 mm mrad/hr
Emittance evolution at the start of the store
BBComp experiments have been performed in few stores, TEL-1 was needed to clean abort gaps.
BBC Team All Experimenter's Meeting - Dec 8, 2007 3
Important changes since then1. New electron guns developed with wider and
more optimized electron beam profiles *2. Orbit stabilization in Tevatron, better beam
diagnostics (bunch-by-bunch 1.7GHz Schottky)3. Much better understanding of beam-beam effects4. TEL-2 built and installed (2006 shutdown) that can
be used for studies ** (TEL-1 still works 24/7 in abort gaps)
5. Ability to use & tune up TEL-2 parasitically in stores at low e-current on a single bunch
6. Beam-beam compensation efforts switched from antiprotons to protons ***
BBC Team All Experimenter's Meeting - Dec 8, 2007 4
Electron guns developed for TELs
E-beam is strongly magnetzed in 2-40 kG
magnetic field
Profile shape inthe interaction region
is the same
Initial (2001)
Used for PbarCompensation (2003)
Used now (2005)
BBC Team All Experimenter's Meeting - Dec 8, 2007 5
TEL-2 in the tunnel (A0)
BBC Team All Experimenter's Meeting - Dec 8, 2007 6
What to compensate? protons or pbars?
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.
Protons Antiprotons
BBC Team All Experimenter's Meeting - Dec 8, 2007 7
TEL-2 e-beam aligned and timed on protons
in space in time
P12P11P10P9
A24
TEL
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.
BBC Team All Experimenter's Meeting - Dec 8, 2007 8
TEL-2 on P12: 1st hour of store #5119
Bunch P12 – TEL-2 acts on it
Bunch P36 – not affected by TEL-2
TEL-2 current
BBC Team All Experimenter's Meeting - Dec 8, 2007 9
TEL-2 improves proton bunch lifetime
BBC Team All Experimenter's Meeting - Dec 8, 2007 10
The improvement is reproducible
Store #5119
Store #5123
Store #5127
BBC Team All Experimenter's Meeting - Dec 8, 2007 11
Why does that happen?
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.
Bunches are not equal! TEL-2 moves Qv up
BBC Team 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.
BBC Team 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