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

SLAC EPAC June 12, PEP-II e + e - Collider

SLAC EPAC June 12, PEP-II is a two ring e+e- asymmetric collider

SLAC EPAC June 12, 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.

SLAC EPAC June 12, 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 7 th station on line. Moved horizontal tunes to the half integer. LER horizontal beta-beats much better.

SLAC EPAC June 12, 20036

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8 PEP-II Monthly Peak Luminosity

SLAC EPAC June 12, PEP-II Daily Int. Luminosity

SLAC EPAC June 12, PEP-II Integrated luminosity

SLAC EPAC June 12, PEP-II Delivered Luminosity in 2003

SLAC EPAC June 12,

SLAC EPAC June 12, 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.

SLAC EPAC June 12, Predicted Integrated Luminosity FY2003

SLAC EPAC June 12, 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.

SLAC EPAC June 12, Luminosity Equation  y is the beam-beam parameter (~0.06) I b 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)

SLAC EPAC June 12, 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 =0.52  0.51). Improve injection efficiency and rate. Lower BaBar backgrounds. Reduce component HOM heating. Reduce the Electron Cloud Instability (ECI)

SLAC EPAC June 12, 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 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.

SLAC EPAC June 12, 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.

SLAC EPAC June 12, 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

SLAC EPAC June 12, 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

SLAC EPAC June 12, Octupole Magnets (from CERN)

SLAC EPAC June 12, 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

SLAC EPAC June 12, Old Longitudinal Kicker

SLAC EPAC June 12, New Longitudinal Feedback Kicker Assembly

SLAC EPAC June 12, New Longitudinal Feedback Kicker End Plug

SLAC EPAC June 12, Transverse Feedback Kicker

SLAC EPAC June 12, 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

SLAC EPAC June 12, 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

SLAC EPAC June 12, 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,…

SLAC EPAC June 12, Meters Centimeters Possible 2x10 34 Interaction Region with a ±3.25 mrad Xangle M. Sullivan Jun. 14, 2000 QD1 QD4 QF5 QF2 QD4 QF5 QD1 QF2 Extra focusing Extra focusing 3.1 GeV 9 GeV PEP-II upgrade with Permanent Magnet Quadrupoles

SLAC EPAC June 12, Path to higher PEP-II luminosity Luminosity5.2E337.5E331.5E342.5E34Units I mA I mA Beta y* mm Beta x* cm Bun. Length cm # bunches Vert. emit nm Horiz. Emittance40/5035/4535/4540/53nm (+/-) Crossing angle000+/-4 (?)mrad Beam-beam para.(x/y)7.5/4.27.5/4.47.5/5.68.2/5.8x100 Number RF stations Date hardware readyNov 02Mar 03Nov 05Nov 07 Date for luminosityMar 03Dec 03Fall 06Fall 08

SLAC EPAC June 12, 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

SLAC EPAC June 12,

SLAC EPAC June 12, PEP-II Summary PEP-II has delivered 33 fb -1 so far in Run 3 and a total of 135 fb -1 since May 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 x cm -2 s -1. More machine studies will help. Upgrades for Summer FY2003 are on track. There are long range plans leading towards L >2 x cm -2 s -1.

SLAC EPAC June 12, KEKB PEP-II Comparison of KEKB and PEP-II to date

SLAC EPAC June 12, PEP-II and KEKB Possible Luminosity Gains (estimated by J. Seeman June 2003) EffectPEP-IIPEP-II GainKEKBKEKB Gain Lower  y * 12  7 mm  6 mm 1.0 Move x tune to 0.52In progress1.0Done1.0 Move x tune to 0.505Later1.2In progress1.1 Increase currentsIn progress2.0In progress1.3 Stronger LER solenoidsIn progress1.4In progress1.2 X-angle or Crab cavitiesNot needed1.0 (1.1) (2.0) Increased injection rate 30  60/ Done (50 Hz) 1.0 Or Continuous injectionNeeds study1.1 (1.2)Needs study1.05 Or two bunch injectionNeeds study1.1Done1.0 Total factor75% of gain4.2 (5.0)75% of gain2.0 (2.7)

SLAC EPAC June 12,

SLAC EPAC June 12, K. Oide’s Prediction of KEKB’s Integrated Luminosity