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)

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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

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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

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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.

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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