Accelerator Systems Division

PEP-II Accelerator Status
John Seeman
Particle and Particle-Astrophysics Directorate
Stanford Linear Accelerator Center
KEKB ARC Meeting
March 20, 2007

Accelerator Systems DivisionTopics• Major new hardware items from Fall 2006
down.
• Accelerator issues in January to March.
• Present luminosity plots• Schedule for Run 6• Activities for Fall 2007 down
• Turn off PEP-II September 30, 2008

Accelerator Systems Division

PEP-II e+e- Collider Overview•BaBar
Detector

Accelerator Systems Division

The PEP-II Team•

Accelerator Systems Division
SLAC Support GroupsBaBar
LBNL
ILC
Machine Advisory Committee1x1034

Accelerator Systems Division

PEP-II Interaction Region Components near BaBarLERHERBaBar

Collision point

Accelerator Systems Division

How the beams enter and exit the PEP-II Interaction Region

Accelerator Systems Division

Quick update facts for PEP-II for Run 5b and Run 6• Peak luminosity= 1.00  1.20 x 1034.
• Best integrated shift = 247  339 pb-1.
• Best integrated 24 hrs = 728  911 pb-1.
• Specific luminosity at high current ~3.6  4.1.
• Fall “2006 down” August 18 to Jan 12• Run 6 turn-on in January seemed slow but is about“average.”Accelerator Systems Division

Accelerator Improvement Projects for Fall 2006•••••••••••••X-Y BPM upgrades
New HER Q5 vacuum chambers
HER-10 RF station
HER-11 RF station
HER power supply upgrade for higher tunes
New HER Q4 vacuum chambers
New IR2 Q2 bellows
LER IR HOM absorber
HER IR HOM absorber
LER BPM monitor upgrade
LER new high power bellows
LER NEG vacuum chamber upgrade
New Longitudinal feedback processor

2006 Done2006 Done2006 Done2006 Done2006 Done2006 Done2006 ½ done
2006 Done2006 Done2006 5/6 done
2006 Done2006 Done2006 DoneAccelerator Systems Division

LER Forward Q4 Location•

Accelerator Systems Division

LER/HER Q2 IR Vacuum Chamber (Fall 2006March 2006)

Thermal analysis of synchrotron
radiation power (~100 W/cm)

S. Metcalfe

NEGVacuumPump

High power separation chamber

Accelerator Systems Division•Accelerator Systems Division“Discharge” on Absorbing Tile•
SiC/AlN
HOM Tile

Arc siteCu heat sinkRF seal fingers

Accelerator Systems Division

New RF seal to correct problem:
New seat on Cu base not tile•

N. Kurita

Accelerator Systems DivisionNew HOM bellows install Fall 2006•

Tiles behindFingers
N. Kurita
Novokhatski
Weathersby
April 2006

Accelerator Systems Division

Example: HER QF5R Chamber (Fall 2006)
SpecificationsConstruction

R. PopeDesign

Accelerator Systems Division

RF Cavity Production•
ACCEL Germany

Finished cavity

Ports to be welded
Cavity bowls welded together.
Installed in November 2006.

H. Schwarz, A. Hill

Accelerator Systems Division

B-Factory RF Klystrons (1.2 MW) under construction•C. Pearson

HER has all SLAC klystrons now!

Accelerator Systems Division

PEP-II RF Cavities

Accelerator Systems Division

New LER Beam Position Monitors• ~700 BPM buttons changed during the Fall down.
About 150 to go!

New button design
HOM absorber
Button puller design

N. Reeck
M. Kosovski
N. Kurita

Accelerator Systems Division

New HOM absorber near IR2 gate valve
Elliptical to
Octagonal
Transition(Existing)Absorber
Octagonal to
LER Arc
Transition (New)Accelerator Systems Division

Fire Recovery from August 18.
•Fire damaged cables
repaired with hard
work from Power
Conversion andControls Departments.
Preventative measuresinstalled. Should not
happen again.

Accelerator Systems Division

Good day in Summer 2006

Accelerator Systems Division

Future PEP-II Overall Parameters and Goals
Parameter

Units

DesignPresent best

2008 goal

I+mA

2140

2940

4000

I-mA

750

1940

2200

1658

1722

1732

Numberbunches

βy*mm

15-20

108

Bunch lengthmm

1511-1290.03

ξy0.047-0.065 0.054-0.07

Luminosity

x1033

31220

Int lumi /daypb-1

130

911

1300

4 times design

7 times design

Accelerator Systems Division

Run 6 January-February Issues• The shut down extended a week longer to get allitems done.
• RF stations were more difficult to turn-on thanusual (+ two new ones). Many small items.
• A re-installed gate valve still over heated evenwith new HOM damping unit nearby and had tobe removed.
• Two vacuum leaks in Region 6 had to be fixed.
• Pulled off BPM button heads in IR2 needed newamplifiers installed for ones with “broken pins.”

Accelerator Systems Division

Luminosity March 18, 2007•

Accelerator Systems Division

Last 24 hours•

Accelerator Systems Division•Accelerator Systems Division•Accelerator Systems Division

Specific Luminosity March 2007 vs Aug 2006•
Sp. Lum 10% down

Accelerator Systems Division•Accelerator Systems Division

Detector Dead Time (~2 %) in Continuous Injection•Accelerator Systems Division

Near term activities• Reduce number of RF trips• Raise the beam currents.
• Move LER horizontal tune closer to half
integer tune by lowering the “beta beats”• Introduce the 90 degree lattice HER for
shorter bunches• Lower βy*• Lower LER vertical emittanceAccelerator Systems Division

PEP-II MAC: Reduce Vertical Emittances  Decker studies

F-J. Decker

Collision point
SK6

SK5IR2 Straight

SK5LSK6L

Accelerator Systems Division

Formula used for H_y:Y. Nosochkov:

Formula used for H_2:

Valeri Lebedev:

Accelerator Systems Division

New skew magnets to cure LER Vertical Emittance10 to 50% gain at fixed currents
Physicist design (F-J. Decker)(Ready to go this week!)
Final mechanical design (Kharakh)

Accelerator Systems Division

PEP-II Utility work in late March 2007 (3 days) for LCLS

•LCLS
tunnelPEP-II coolingwater andair lines

Accelerator Systems Division

LCLS Tunnel Elevation View•

Accelerator Systems Division

Integrated Luminosity Projection from Summer 2006

•Goal = 940 fb-12007Down2006
DownNowAccelerator Systems Division

Fall 2007 Down Activities (September 1-November 28)•••••

Finish LER BPM replacement if not done during Run 6.
Install IR2 backward Q1-Q2 bellows unit.
Replace about 10 to 20 HER Arc bellows units
Replace 10 to 20 HER Arc “Omega Seals”.
Install collimator in IR2 downstream LER if needed for
reduced backgrounds.
• Install several LER higher HOM bellows.
• Install two new LER Q5 chambers in IR2.

Accelerator Systems DivisionConclusions
PEP-II turn-on for Run 6 is about average historicallyalthough it seems more difficult.
The luminosity will be ramped as fast as possible (now0.97 x1034) with the aim of about 1.7 this run.
Integrate-Integrate-Integrate!
Planning for the Fall 2007 down has started.
Upgrades towards ~2×1034 are mostly done.
Run plans are in place with target of about 1 ab-1 at theend of FY2008.
Turn off PEP-II September 30, 2008!