PEP-II Status and Outlook John T. Seeman For the PEP-II Team SLAC EPAC Meeting June 12, 2003.

PEP-II Status and Outlook

John T. Seeman

For the PEP-II Team

SLAC EPAC Meeting

June 12, 2003

SLAC EPAC June 12, 2003 2

PEP-II e+e- Collider

•


PEP-II is a two ring e+e- asymmetric collider


PEP-II Run for FY2003

• Turned on November 15, 2002, after a 3.5 month down.• Storms in December caused power outages and component damage.• Winter-spring run is going well, in general.

– Exceptions: three IR vacuum leaks, lost a 1.2 MW klystron, many RF trips (aborts) (but getting better), many HER IR “dust” events causing radiation aborts.

• Integrated luminosity is on track reaching a total of 135 fb-1.• Luminosity is increasing with new records every few weeks.• Will turn off PEP-II on June 29.• Will turn on September 8, 2003 for a ten month run.


Recent Accelerator Advances

• By-3 bunch pattern has worked well.• Orbit bumps in sextupoles helps coupling.• Shorter abort gap (2.5%) works helping RF transients.• Three LER RF stations and six HER RF stations in use

– Didn’t get HER 7th station on line. • Moved horizontal tunes to the half integer. • LER horizontal beta-beats much better.


PEP-II Monthly Peak Luminosity

Peak PEP-II Luminosity (x1E33) per Month

0

1

2

3

4

5

6

7

Jun-

99

Dec

-99

Jun-

00

Dec

-00

Jun-

01

Dec

-01

Jun-

02

Dec

-02

Jun-

03


PEP-II Daily Int. Luminosity

PEP-II Daily Average for each Month

0

50

100

150

200

250

300J

an

-99

Ap

r-9

9

Ju

l-9

9

Oc

t-9

9

Ja

n-0

0

Ap

r-0

0

Ju

l-0

0

Oc

t-0

0

Ja

n-0

1

Ap

r-0

1

Ju

l-0

1

Oc

t-0

1

Ja

n-0

2

Ap

r-0

2

Ju

l-0

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Oc

t-0

2

Ja

n-0

3

Ap

r-0

3

pb

-1


PEP-II Integrated luminosityPEP-II Monthly Integrated Luminosity

0

1000

2000

3000

4000

5000

6000

7000

8000

Jan

-99

Mar

-99

May

-99

Jul-

99

Sep

-99

No

v-99

Jan

-00

Mar

-00

May

-00

Jul-

00

Sep

-00

No

v-00

Jan

-01

Mar

-01

May

-01

Jul-

01

Sep

-01

No

v-01

Jan

-02

Mar

-02

May

-02

Jul-

02

Sep

-02

No

v-02

Jan

-03

Mar

-03

May

-03

pb

-1


PEP-II Delivered Luminosity in 2003

PEP-II Total Delivered Luminosity for 2003

0

5000

10000

15000

20000

25000

30000

35000

400003

1-D

ec

30

-Ja

n

1-M

ar

31

-Ma

r

30

-Ap

r

30

-Ma

y

29

-Ju

n

Time

pb

-1

32.5 fb- 1

Grand total delivered 135 fb- 1


Near Term Luminosity Improvements to PEP-II

• New ring correction algorithms (MIA) –Now works globally to fix beta beats and coupling. So far does not work locally (IR). Next fix HER horizontal beta beats.

• New local y* knobs in HER and LER. Try for 9 mm.• Increase number of bunches and currents. Need to watch

RF trips, vacuum heating, and backgrounds.• Reduce HER emittance and raise LER emittance.• Try continuous injection.


Predicted Integrated Luminosity FY2003


Overall plans to improve the PEP-II program

• Increase machine studies from 5% toward 15%.• Restart the PEP-II Machine Advisory Committee with

the chairman David Rice (Cornell). (First meeting set tentatively for October 9-11, 2003).

• Perform a Mid-Project Evaluation with PEP-II people and outside-the-project people to refine our tasks.

• Welcome further participation of BaBar collaborators.• Increase activities of the PEP-II RF Task Force.


Luminosity Equation

y is the beam-beam parameter (~0.06)

• Ib is the bunch current (1 ma x 2 ma)

• n is the number of bunches (~942)y

* is the IP vertical beta (~12 mm)

• E is the beam energy (3.1 and 9 GeV)

*341017.2

y

byEInxL


Overall goals for next year

• Raise HER beam current to 1.5 amps (now 1.1 amp).• Raise LER current to 2.7 amps (now 1.6 amps).• Increase number of bunches (942 1150).• Lower y

* from 12 9 mm.• Raise the beam-beam parameter

– (move to x=0.520.51).

• Improve injection efficiency and rate.• Lower BaBar backgrounds.• Reduce component HOM heating.• Reduce the Electron Cloud Instability (ECI)


Raise HER and LER currents

• HER has seven RF stations with six in use. One missing a klystron. We will add one more station this summer.

• LER has 3 RF stations, all in use. We will add a LER station in Summer 2004.

• New low level RF controls and feedback now coming on line.

• Still too many trips of RF stations. Trip rate is the same as last year but the beam currents are 15% higher.

• Two new klystrons and two repaired klystrons should arrive in the next six months.


Increase the number of bunches

• The luminosity can be increased by adding bunches.

• If the bunch charges remain the same, the beam-beam effects are unchanged and the luminosity increases linearly with current.

• Higher current beams increase heating issues in the vacuum chambers.

• Increased currents mean that the RF system must handle more current loading but with added stability.

• The bunch-by-bunch feedback systems also must work harder and closer to specifications.

Luminosity along the train with By-3 bunch pattern and mini-gaps.


Lower y* in HER and LER

• Lowering y* will increase the luminosity. Try for 12 9 mm.

• Must locally correct the coupling and energy dispersion in the IR after beta reduction.

• Must reduce the bunch length at the same time. We will raise RF station voltages and increase the number of RF stations.

Nominal

With Hourglass


Increase the beam-beam parameter

• We will increase the beam-beam tune shift by moving to a better tune location and by weakening beam-beam resonances.

• Moving the horizontal tune closer to the half integer allows the dynamic beta effect to increase the tune shift.

• However, near the half integer beta-beats from quadrupole errors are worse and must be corrected.

• First MDs this week to move the LER first has gone well. Will soon move the HER to the half integer.

• The LER will be done first as the HER is stronger in collisions.

LER tune plane vs. luminosity plot


Octupole Magnets (from CERN)


Lower BaBar backgrounds

• BaBar backgrounds are often good.• Backgrounds can be poor during

injection (mostly HER) and at high currents and luminosity.

• Muon IFR outer layers are often swamped.

• A new HER upstream collimator will be installed this summer.

• In LER Pb shielding will be installed upstream to reduce IFR beam spray.

• Injection studies are being planned to improve reliability.

HER horizontal collimator


Old Longitudinal Kicker


New Longitudinal Feedback Kicker Assembly


New Longitudinal Feedback Kicker End Plug


Transverse Feedback Kicker


Reduce the Electron Cloud Instability (ECI)

Low energy electrons in the vacuum chamber are attracted to the positron beam and cause “head-tail” instabilities. This is called ECI.

Solenoids have been shown to strongly reduce this effect in PEP-II by keeping the electrons near the chamber walls. This summer we plan to strengthen the solenoids in the straight sections (x 3 in field) so that bunches can be placed every 2 RF buckets (every 3 now). A chamber distance of about 1 km is to be wound.

ECI in the By-2 bunch pattern


PEP-II Summer 2003 Projects

• New HER # 8 RF station (+200 mA).• New HER collimator (30 m upstream).• New Longitudinal feedback kickers.• Improved transverse feedback kickers.• Improved low level RF feedback circuits (higher I).• More x-y BPMs in IR2 region.• LER straight section and Arc 11 solenoid upgrade.• Octupoles for tune shift with amplitude studies.• Bellows fans on all LER bellows (~240)• Fix IR vacuum gate valves • Air cooling of Feedback Kicker cables• More background shielding of PEP-II in IR2• IR4 HOM damper


FY2004 and longer plans

• Continue to increase luminosity each year AIP funding (Accelerator Improvement Projects)

• Big upgrade in the summer of FY 2005 by moving quadrupoles closer the the interaction region and lowering y

* to 6-7 mm.

• Continue to add RF stations (one station per year for five years)

• Some higher power vacuum chamber upgrades needed.

• Better beam controls needed: bunch-by-bunch feedbacks, injection, backgrounds, Electron Cloud Instability,…


0 2.5 5 7.5-2.5-5-7.5

0

10

20

30

-10

-20

-30

Meters

Cen

time

ters

Possible 2x1034 Interaction Region with a ±3.25 mrad Xangle

M. Sullivan Jun. 14, 2000

QD1

QD4QF5

QF2

QD4 QF5

QD1 QD1

QD1

QF2

Extra focusing

Extra focusing

3.1

GeV

3.1

GeV

9 GeV

9 GeV

PEP-II upgrade with Permanent Magnet Quadrupoles


Path to higher PEP-II luminosity

• Luminosity 5.2E33 7.5E33 1.5E34 2.5E34 Units• I+ 1850 2400 3300 4500 mA• I- 950 1250 1600 2000 mA• Beta y* 12 10 8.0 6.5 mm• Beta x* 50 50 50 50 cm• Bun. Length 1.2 1.05 0.9 0.8 cm• # bunches 942 1180 1450 1700• Vert. emit 2.5 1.4 0.9 0.9 nm• Horiz. Emittance 40/50 35/45 35/45 40/53 nm (+/-)• Crossing angle 0 0 0 +/-4 (?) mrad• Beam-beam para.(x/y) 7.5/4.2 7.5/4.4 7.5/5.6 8.2/5.8 x100• Number RF stations 9 10 13 15• Date hardware ready Nov 02 Mar 03 Nov 05 Nov 07• Date for luminosity Mar 03 Dec 03 Fall 06 Fall 08


Long Range PEP-II Upgrades

• Over the next 4 years PEP-II will add:– Four RF stations– Reduce y* from 12 mm to about 6.5 –7.5 mm– Somewhat better bunch-by-bunch feedbacks– Bellows cooling– Higher power vacuum chambers in the IR– Move quadrupoles closer to the IR but still permanent magnets– More and stronger sextupoles– More collimators– Better injection background hardware– More vacuum chamber solenoids


PEP-II Summary

• PEP-II has delivered 33 fb-1 so far in Run 3 and a total of 135 fb-1 since May 1999.

• PEP-II is starting to take advantage of the FY2002 summer down projects. There are several advances to go!

• Integrated luminosity is on the predicted track.• Luminosity has increased to 6.485 x 1033 cm-2s-1. More machine

studies will help.• Upgrades for Summer FY2003 are on track.• There are long range plans leading towards L >2 x 1034 cm-2s-1.


KEKB

PEP-II

Comparison of KEKB and PEP-II to date


PEP-II and KEKB Possible Luminosity Gains (estimated by J. Seeman June 2003)

Effect PEP-II PEP-II Gain KEKB KEKB Gain

Lower y* 12 7 mm 1.5 6 6 mm 1.0

Move x tune to 0.52 In progress 1.0 Done 1.0

Move x tune to 0.505 Later 1.2 In progress 1.1

Increase currents In progress 2.0 In progress 1.3

Stronger LER solenoids In progress 1.4 In progress 1.2

X-angle or Crab cavities Not needed 1.0 (1.1) 2005-2006 1.5 (2.0)

Increased injection rate 30 60/120 1.1 Done (50 Hz) 1.0

Or Continuous injection Needs study 1.1 (1.2) Needs study 1.05

Or two bunch injection Needs study 1.1 Done 1.0

Total factor 75% of gain 4.2 (5.0) 75% of gain 2.0 (2.7)


K. Oide’s Prediction of KEKB’s Integrated Luminosity

PEP-II Status and Outlook John T. Seeman For the PEP-II Team SLAC EPAC Meeting June 12, 2003.

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Transcript of PEP-II Status and Outlook John T. Seeman For the PEP-II Team SLAC EPAC Meeting June 12, 2003.