Accelerator Systems Division

PEP-II ProgressandSLAC Future
John Seeman for the PEP-II Team
Particle and Particle-Astrophysics Directorate
Stanford Linear Accelerator Center
KEKB ARC Meeting
December 4, 2007

Accelerator Systems DivisionTopics• Highlights of PEP-II Run 6.
• Main activities for Fall 2007 down
• Plan for PEP-II Run 7 in FY2008• Shut down planning• Brief SLAC Overview

Accelerator Systems Division

The PEP-II Team•PEP-II MAC
1x1034

Accelerator Systems Division

New Items for PEP-II in Run 6• Advances:– Two new HER RF stations.
– New skew quad fix for IR2 LER x-y coupling foundand implemented. Specific luminosity is higher.
– Fast dither IP feedback in and working (10 Hz).
– Vertical vibration in IR support tube damped withBaBar’s help.

• Problems:– Vacuum leak in HER IR Q4 chamber– Damaged coils on IR Quadrupole Q2– HER flex-flange seals show discharges– More PG&E site wide AC power dips than normal.

Accelerator Systems Division

HER Flex flange RF seal

Accelerator Systems Division

Example of a melted RF seal
These GlidCopfingers are brazed
onto the SSmounting plate

Inside of ringAccelerator Systems Division

Two-gap model of a cavity

Omega seal

left gap

right gap

Novokhatski

Accelerator Systems Division

New RF Seal Design:
Installed 187 New Seals in Fall 2007
Same as the old design but
omega fingers made out ofsilver plated Inconel. Theentire SS plate is silver plated.

Accelerator Systems DivisionHER HOM power

Novokhatski

Accelerator Systems Division

LER HOM power in runs

Novokhatski

Accelerator Systems Division

RF LER current limits with new Pre-amplifiers•(Rivetta)

Accelerator Systems Division

Measurement of phase transients along bunch trainLER)
tailheadheadtail

Streak camera image

7.3 µsec(Cheng)Accelerator Systems Division

200ns horizontal scale
Near the bunch train gap, 1722 bunches with 24 bunches gap~ 50ps  8.6 deg

4.2ns

Accelerator Systems Division

Beam Aborts Statistics•

Accelerator Systems Division

Beam Aborts•

Accelerator Systems Division

IP Characterization• Use BaBar’s tracking resolution and prime venue
for measuring important parameters at the IP
e- beam(resolution)
Production vertices (x,y,z ~ 30µm)
Boost trajectories (θ ~ 0.6 mrad)e+ beam– Three analyses each measuring εy, β*y• dLumi / dz vertexing e+e- and µ+µ- events• σyLumi(z) µ+µ- events• σy’Lumi(z) µ+µ- events

Accelerator Systems Division

BaBar IP measurements reported online• Luminous Region}– centroids { x, y, z}– sizes { x, z }every 10 minutes– tilts { dx/dz, dy/dz }– dL/dz fit { Σz, β*y, zw, zc}
every ~hour• Boost Trajectory– mean { x’, y’ }– spread { x’HER, y’HER }every 10 minutes
every 30 minutes

Accelerator Systems Division

Bunch Length Extraction from dL/dz Fits

βy* = 13mm
ΔΣz2 = 10.3 mm2 ± 0.4 mm2σ z, H

10.9 mm ± 0.2 mm
10.4 mm

σ z, L10.8 mm ± 0.2 mm

Σz (mm)ΔVRF

BaBar Run

Accelerator Systems Division

IP Beta Function Measurements (BaBar)dL /dz

σyL

σy’B

PEP
phase
advanceβ2

Accelerator Systems Division

New Skew Magnets to Improve LER
Vertical Emittance10 to 50% gain at fixed currents

Physicist design (F-J. Decker)

Accelerator Systems Division

HER emittance on July 18 (red), 2007

Accelerator Systems Division

LER emittance in July, 2007

Accelerator Systems Division

Record peak specific luminosity obtained in 2007
after reducing LER coupling for lower Y emittanceManaged to get a peakspecific luminosity (asshown on red) with alower LER current.

28-aug 9:00am,peplog

Accelerator Systems Division

Specific Luminosity in PEP-II•
By-2(By-4)

Accelerator Systems Division

Run 6 nos.
11.69

2650x1900

311858

Accelerator Systems DivisionAccelerator Systems DivisionAccelerator Systems Division

August 2007 was our Best month

New monthand 30 dayrecords

Accelerator Systems Division

A look at the timeline of BaBar data collection vs physics outputFromBaBar•There are more than 200 ongoing analyses of BaBar data.
•More than 317 papers published & submitted for publication.

Accelerator Systems Division

PEP-II Parameter Goals have not changed!
Parameter

Units

DesignPresent best

2008 goal

I+mA

2140

2940

4000

I-mA

750

1940

2200

1658

1722

1740

Numberbunches

βy*

mm

15-20

108-8.5

Bunch length

mm1511-12

8.5-90.03

ξy0.047-0.065 0.054-0.07

Luminosity

x1033

3

1220

Int lumi /daypb-1

130

911

1300

4 times design

7 times design

Accelerator Systems Division

Fall 2007 Down Activities (September 4-December 3)••••••

Finished LER BPM replacement.
Added 5 HER Arc HOM bellows.
Added 12 LER IR2 HOM bellows.
Replaced 187 HER Arc flex-flange RF “Omega Seals”.
Installed two new LER Q5 chambers in IR2.
Installed repaired HER Q4L chamber.

Accelerator Systems DivisionInteraction Region Layout
Summer 2007 shutdown work
BaBar detector
LER Frang. Link
modifiedHER Frang. Link
replaced

LER Q5L replaced

LER Frang Link
replacedLER
LER Q5R replaced

HER Q4L repairedHER

Accelerator Systems Division

Side view of BaBar
Q2 magnetAccelerator Systems DivisionHER Q4L chamber•Installed new, larger aperture, Al chamber during 2006 down
•Flexflange weld failed April 2007, temporary repair with Vacseal•Removed Al chamber and reinstalled old StSt chamber while Al chamber
repaired•Flexflange replaced with fixed flange
Old StSt chamber

New Al chamber

Accelerator Systems Division

HOM absorbing bellows Components
Restraint

Welded Bellows

OFE Cu Prong Body
Ceralloy Tile
SST Water
Jacket Cover
SST Prong Support

Glidcop StubJ-SealGlidcop RF Fingers

Inconel SpringFingers

Accelerator Systems Division

HOM absorbing bellows
In IR 2 we are replacing 5 bellows
sections in the upstream LER andHER and 7 units in thedownstream LER with bellows
modules that contain HOM
absorbing tiles. We hope toreduce the HOM power in this area

Novokhatski
Weathersby
KuritaReeck
Metcalfe

Absorbing tiles

Accelerator Systems Division

General Overall Plan for Run 7 (Dec 2007-Sept 2008)• Start the linac and PEP-II on December 7.
• Run through the holidays.
• Do more machine studies (MD) early toincrease luminosity at the beginning of therun.
• Find the optimum luminosity condition byearly spring.
• Run through September 30 with best steadystate conditions.

Accelerator Systems Division•NowAccelerator Systems Division

PEP-II Shut Down
• PEP-II will stop producing data for BaBar on
September 30, 2008, about ten months from now.
• PEP-II and BaBar will then transition rapidly intoa “Minimal Maintenance State (MMS)” whichtakes just over a year.
• In the medium time frame, PEP-II will be at thisMMS with some effort going into tunnel
maintenance, safety lighting, electrical safety andmechanical safety. Valuable items will bepreserved.
• For long term, D&D of PEP-II is being studied. ADOE review was held August 6-7, 2007.

Accelerator Systems Division

SLAC Future Options• Ongoing programs: ILC, PEP-II, SPEAR-3,ATLAS, LARP, Astrophysics, EXO-200• Near term projects: LCLS
• Possible future projects: LSST, SNAP,ATLAS upgrades, LCLS upgrades, PEPLS, LHC upgrades, High Gradient program,
EXO2000, Super-B, …
• SLAC has started a long range planning
exercise looking at these future projects.
Study not finished yet.

Accelerator Systems Division

Super-B Factory Design•••

SLAC is contributing modestly to the design
effort for a Super-B Factory. Helped produce aDesign Report in Spring 2007 (SLAC ReportR-856). The goal is a factor of 100 increase inluminosity over PEP-II. Uses “ILC-like”
damping rings with very small emittances,crab-waist at the IP, and smaller beam currents
to save power.
Supporting modestly the effort of INFN inItaly leading towards a Super-B accelerator
and detector to be built near Rome.
SLAC could consider contributing in-kindaccelerator and detector components after
September 2008 when PEP-II and BaBar are
turned off. Perhaps starting in FY2011.

Accelerator Systems Division

LCLS Progress••••••••

Injector installed Spring 2007.
Injector and first bunch compressor
successfully tested by August 2007.
Beam achieved 15 GeV.
Second bunch compressor installed
Fall 2007.
New compressor will be tested January
2008.
Downstream LCLS with undulator tobe installed spring-Fall 2008 andcommissioned in December 2008.
First users in Summer 2009.
Full set of users in Spring 2010.

Accelerator Systems Division

PEP-II Conclusions
PEP-II accelerator in Run 6 was more difficult thanplanned but the run ended well.
Execution of the Fall 2007 shut down went well.
Upgrades towards ~2×1034 are done with the aim of 250
fb-1 more to 750 fb-1 total.
The luminosity will be ramped as fast as possible inRun 7.
PEP-II will integrate as much luminosity as possible.
PEP-II will turn off September 30, 2008.