PEP-II in Run 7 and Transition Planning

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PEP-II in Run 7 and Transition Planning

• John T. Seeman
• Assistant Director PPA/LCLS

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Talk Overview

• Brief PEP-II Layout
• Run 7 operations
• Transition planning
• PEP-II Minimum Maintenance State
• Future possibilities for PEP-II tunnel and
  hardware

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PEP-II Mission in FY2008

• To provide ee- collisions to the BaBar Detector
  to carry out B-meson and other physics
• Advance the State of the Art for accelerator
  physics for high luminosity colliders
• Enter a Minimum Maintenance State after the
  collider programs terminates.
• Start the study for Deactivation and
  Decommissioning.

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The PEP-II Team
PEP-II was constructed by SLAC, LBNL, and LLNL
with help from BINP, IHEP, BaBar
collaboration. Many thanks to the US Department
of Energy And Machine Advisory Committee.

1x1034
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Brief PEP-II History

• 1987 Physics asymmetrical energies helps
  separate B mesons.
• 1991 First PEP-II CDR.
• 1993 Second CDR (9 GeV x 3.1 GeV).
• 1994 Construction started.
• 1997 First stored HER e- beam.
• 1998 First stored LER e beam.
• 1998 First collisions July 23, 1998, at 1205
  pm.
• 1999-2007 Y4S data for BaBar (433 fb-1)
• 2008 Y2S (30 fb-1), Y3S (15 fb-1), and small
  energy scan for BaBar.
• 2008 Turned off PEP-II April 7, 2008, at 1122
  pm
• just after setting an e current world
  record (3.2 A).
• 1999-2008 Total delivered integrated luminosity
  557.4 fb-1.

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PEP-II Layout

Two rings Circumference 2.2 km.
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B-Factory Overall Parameters

• Parameter PEP-II
• (LER/HER)
• Circumference (m) 2200
• Beam energy (GeV) 3.1/9.0
• Number of bunches 1732
• Beam currents (A) 3.2/2.0
• Horizontal emittance (nm) 30/45
• by (mm) 9/11
• xy 0.06/0.05
• IP beam sizes (microns) (x/y) 120/4
• Luminosity (x 1033/cm2/s) 12.1

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The PEP-II Collider
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PEP-II Interaction Region Components near BaBar
BaBar Detector
LER
HER
BaBar
Collision point
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How the beams enter and exit the PEP-II
Interaction Region
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IR Permanent Magnets
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Interaction Region Support Tube
Be chamber
Silicon Vertex Tracker SVT
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What worked with the PEP-II Accelerator design?

• All components as designed worked to get above
  the design luminosity parameters (magnets, RF
  system, vacuum system, interaction region,
  background mitigation, beam instabilities,
  bunch-by-bunch feedbacks, injection, controls)
• Major changes to get to x 4 luminosity and x 7
  integrated luminosity
• Electron cloud instability needed 30 gauss
  solenoids on LER
• Added cooling on IP Be chamber bellows.
• Improved masking near IR
• Added 7 RF stations to handle added current.
• Improved feedback kickers
• Improved RF controls
• Higher power vacuum expansion bellows
• Continuous injection mitigation
• Shorten abort gap (3 to 1)
• Improved quadrupole lattices
• Improved x-y coupling control

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PEP-II RF Cavity
Early design and testing at LBL. High power
production cells. Fully fitted cavity units with
HOM dampers.
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B-Factory RF Klystrons (1.2 MW)

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HOM Absorbing Bellows

Shield fingers
HOM tiles
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Running before Trickle (Continuous) Injection

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Continuous Injection for PEP-II

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Luminosity Equation for a Circular ee- Collider

• xy is the beam-beam parameter (0.06)
• Ib is the bunch current (1 to 3 mA)
• n is the number of bunches (1700)
• by is the IP lattice optics function (vertical
  beta) (10 mm)
• E is the beam energy (3.1 and 9 GeV)
• (9 GeV varied to change Upsilon resonances.)
• Luminosity (1033 cm-2 s-1)

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Beam-beam parameters
sy 3.5-4.3 mm. xy 0.05-0.06 xx 0.03-0.09

By 4 Extended
By 2
I- increases LER y size. I increases LER x
size. I increases HER y size.
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PEP-II Parameters for 3.1 GeV x 9.0 GeV
Parameter Units Design April 2008 Best Factor over Design
I mA 2140 3210 X1.50
I- mA 750 2070 X2.76
Number bunches 1658 1732 X1.04
by mm 15-25 9-10 1/2.0
Bunch length mm 15 11-12 1/1.42
xy 0.03 0.05-0.06 X2.0
Luminosity X1033/cm2/s 3 12 X4.0
Int lumi / day pb-1 130 911 X7.0
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Upsilon Resonances

• To change center-of-mass energy, PEP-II changed
  HER energy (8.0 to 10.1 GeV) but not LER due to
  permanent magnet focusing in the interaction
  region.

Resonance Data HER Energy
Y2S 14.5 fb-1 8.1 GeV
Y3S 30 fb-1 8.4 GeV
Y4S 433 fb-1 9.0 GeV
Scan above Y4S (5 MeV steps) 4.6 fb-1 8.9 to 10.1 GeV
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PEP-II Peak Luminosity by Month (1999-2008)

Design
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Design of 135 pb-1
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PEP-II total integrated luminosity 557 fb-1
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PEP-II Uptime and Luminosity Integration vs
Milestones

Uptime DOE Milestone Uptime PEP-II Actual Uptime Ratio PEP/DOE Integr. Lumin. DOE Milestone Integr. Lumin. PEP-II Actual Int. Lum. Ratio PEP/DOE
FY2002 80 84.0 1.05 35 fb-1 49.0 fb-1 1.40
FY2003 80 82.4 1.03 45 fb-1 39.9 fb-1 0.89
FY2004 80 88.8 1.11 45 fb-1 114.4 fb-1 2.54
FY2005 80 42.7 0.53 50 fb-1 53.5 fb-1 1.07
FY2006 80 82.4 1.03 100 fb-1 100.3 fb-1 1.00
FY2007 80 81.1 1.01 130 fb-1 90.2 fb-1 0.69
FY2008 80 85.4 1.07 30 fb-1 57.2 fb-1 1.91
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PEP-II General Accelerator Achievements

• Introduced beta-beats to help chromatic
  corrections near IR.
• First collider to continuously inject into a ring
  with the physics detector taking data.
• Installed 2 km of solenoids on the e LER ring to
  suppress the Electron Cloud Instability ECI.
• Held the overall luminosity record for several
  years. Now second to KEKB (1.2 vs 1.7 x 1034)
• Highest stored electron current (2.1 Amps)
• Highest stored positron current (3.2 Amps)

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Transition planning

• PEP-II Run 7 ended April 7, 2008.
• PEP-II has since been kept under PPS (safety)
  control.
• Only a very few parts have been removed for other
  programs.
• Power usage has been minimized.
• Venting, coil drying, and component removal will
  proceed as approval, funding, and manpower is
  available.
• Staff
• Operators have all moved to LCLS operation.
• Engineering staff moved to PEP-II minimum
  maintenance state, LCLS upgrades and maintenance,
  FACET, and PEP-X.
• Physicists have moved to LCLS operations, PEP-II
  minimum maintenance state, FACET, PEP-X, and
  Super-B.
• Operational PEP-II staff level (before April 7)
  250 FTEs
• Present PEP-II staff level (after April 7) 5
  FTEs.
• Power
• Operational power 42 MW
• MMS power 1.8 MW

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Budgets for PEP-II MMS and DND planning
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Future Potential Users of PEP-II Components

• LCLS a few small parts corrector power
  supplies, gate valves, vacuum gauges, wire
  scanners,
• SPEAR-3 a few small parts Loss monitors, streak
  camera, Bergos position monitor electronics.
• PEP-X Tunnel, 6 RF stations, support building,
  e- injection line
• Super-B All magnets, all power supplies, all
  electronics modules, 10 RF stations, all
  supports, all vacuum chambers
• Project X Magnets with vacuum chambers for
  transport lines
• LBNL ALS Chopper power supplies for ALS bends
• J-Lab Electro-magnets for energy upgrade

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PEP-X (SLAC Today July 3)
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PEP-II 1998-2008 Thanks to all!