Round Beam Collisions at VEPP-2000

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Round Beam Collisions at VEPP-2000
                         
Dmitry Berkaev, Alexander Kirpotin, Ivan Koop,
Alexander Lysenko, Igor Nesterenko,Alexey
Otboyev, Evgeny Perevedentsev, Yuri Rogovsky,
Alexander Romanov,Petr Shatunov, Yuri Shatunov,
Dmitry Shwartz, Alexander Skrinsky, Ilya
Zemlyansky
Novosibirsk 21.09.2011
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Layout of VEPP-2000 complex
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Collider overview
L 24.39 m facc 172 MHz Vacc 120 kV E0.2 1
GeV Bbend 2.4 T Bsol 13 T ß2 10 cm ss
3 cm e1.410-7mrad ?x,z 2.1 4.1 a 0.036 ?
0.15 N 1011 L11032cm-2s-1
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The Concept of Round Colliding Beams

• Small and equal ß-functions at IP
• Equal beam emittances
• Equal betatron tunes
• Angular momentum conservation

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VEPP-2000 lattice
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Round beam options


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Positron beam lifetime (I 20 mA)
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Machine tuning

• Closed orbit corrections
• Pick-ups Orbit Response Matrix to focusing
  offsets (4?32)
• SVD analysis steering coil
  corrections
• 2-3 iterations minimizing of ?Icor
  correctors setting
• ?x ?z ? 0.2 mm
• Lattice corrections
• BPMs ORM to steering coils modulations
  (20?36)
• SVD analysis focusing
  corrections (quads solenoids)
• 34 iterations lattice
  setting
• ß zero dispersion outside
  achromats
• Coupling compensation
• 1.5 Tm field of CMD detector solenoids
  compensating coils
• 3 families of skew quads
  ?1 ?2 lt 0.003

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Lattice corrections
ßx, ßz (cm)
ßx, ßz (cm)
after 4 iterations
Dx (cm)
Dispersion
ßx, ßz (cm)
after 3 iterations
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Lattice and beam sizes (I lt1mA)
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Week-strong beam-beam(dynamic beta and
emittance)
I3 mA I-48 mA
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Strong-strong beam-beam(dynamic beta and
emittance)
I61.8 mA I-53.2 mA
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Threshold current vs.tune(week-strong)
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Luminosity measurements
Bhabha scattering in the SND and ?MD
detectors Tscatt 0.5 Main disadvantage ? low
counting rate ? 10 Hz at L11031 cm-2s-1
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Luminosity measurements
(E 837 MeV Run 2011)

L?10-30 (cm-2s-1)
t (sec)
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Luminosity at run 2011 (CMD data)
ramping ?
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Luminosity vs.?
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Positron beam size vs ?
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Radiative polarization
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Beam energy calibration
E 750.67 0.03 MeV
fd (kHz)
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BEP upgrade (1GeV)
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Conclusion

• Round beams give a serious luminosity
  enhancement.
• The beam-beam parameter achieves a value ? 0.15
  .
• VEPP-2000 started up for data taking with 2
  detectors.
• Precise beam energy calibration is in progress.
• To reach the target luminosity, more positrons
  are needed.
• Booster BEP upgrade for beam transfer at 1GeV is
  being prepared.

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Thanks for your attention!
                         
Novosibirsk 21.09.2011