PEPII Status and Outlook John T Seeman For

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

PEP-II e+e- Collider • SLAC EPAC June 12, 2003 2

PEP-II is a two ring e+e- asymmetric collider SLAC EPAC June 12, 2003 3

PEP-II Run for FY 2003 • 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, 2003 4

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, 2003 5

SLAC EPAC June 12, 2003 6

SLAC EPAC June 12, 2003 7

PEP-II Monthly Peak Luminosity SLAC EPAC June 12, 2003 8

PEP-II Daily Int. Luminosity SLAC EPAC June 12, 2003 9

PEP-II Integrated luminosity SLAC EPAC June 12, 2003 10

PEP-II Delivered Luminosity in 2003 SLAC EPAC June 12, 2003 11

SLAC EPAC June 12, 2003 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 by* 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, 2003 13

Predicted Integrated Luminosity FY 2003 SLAC EPAC June 12, 2003 14

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 Ba. Bar collaborators. • Increase activities of the PEP-II RF Task Force. SLAC EPAC June 12, 2003 15

Luminosity Equation • • • xy is the beam-beam parameter (~0. 06) Ib is the bunch current (1 ma x 2 ma) n is the number of bunches (~942) by* is the IP vertical beta (~12 mm) E is the beam energy (3. 1 and 9 Ge. V) SLAC EPAC June 12, 2003 16

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 by* from 12 9 mm. Raise the beam-beam parameter – (move to nx=0. 52 0. 51). • • Improve injection efficiency and rate. Lower Ba. Bar backgrounds. Reduce component HOM heating. Reduce the Electron Cloud Instability (ECI) SLAC EPAC June 12, 2003 17

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. SLAC EPAC June 12, 2003 18

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, 2003 19

Lower b y * in HER and LER Nominal With Hourglass • Lowering b 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. SLAC EPAC June 12, 2003 20

Increase the beam-beam parameter • We will increase the beam-beam tune shift by moving to a better tune location and by weakening 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 betabeats 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, 2003 21

Octupole Magnets (from CERN) SLAC EPAC June 12, 2003 22

Lower Ba. Bar backgrounds • Ba. Bar 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, 2003 23

Old Longitudinal Kicker SLAC EPAC June 12, 2003 24

New Longitudinal Feedback Kicker Assembly SLAC EPAC June 12, 2003 25

New Longitudinal Feedback Kicker End Plug SLAC EPAC June 12, 2003 26

Transverse Feedback Kicker SLAC EPAC June 12, 2003 27

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, 2003 28

PEP-II Summer 2003 Projects • • • • New HER # 8 RF station (+200 m. A). 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 IR 2 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 IR 2 IR 4 HOM damper SLAC EPAC June 12, 2003 29

FY 2004 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 interaction region and lowering by* 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, 2003 30

PEP-II upgrade with Permanent Magnet Quadrupoles Possible 2 x 1034 Interaction Region with a ± 3. 25 mrad Xangle 30 QF 2 20 QF 5 1 3. QD 4 e. V G Extra focusing QD 1 Centimeters 10 9 Ge. V -10 QD 1 Extra focusing -20. 1 3 -30 -7. 5 QD 4 e. V QF 5 G -5 QF 2 -2. 5 0 Meters SLAC EPAC June 12, 2003 2. 5 5 7. 5 M. Sullivan Jun. 14, 2000 31

Path to higher PEP-II luminosity • • • • Luminosity I+ IBeta y* Beta x* Bun. Length # bunches Vert. emit Horiz. Emittance Crossing angle Beam-beam para. (x/y) Number RF stations Date hardware ready Date for luminosity 5. 2 E 33 1850 950 12 50 1. 2 942 2. 5 40/50 0 7. 5/4. 2 9 Nov 02 Mar 03 7. 5 E 33 2400 1250 10 50 1. 05 1180 1. 4 35/45 0 7. 5/4. 4 10 Mar 03 Dec 03 1. 5 E 34 3300 1600 8. 0 50 0. 9 1450 0. 9 35/45 0 7. 5/5. 6 13 Nov 05 Fall 06 SLAC EPAC June 12, 2003 2. 5 E 34 4500 2000 6. 5 50 0. 8 1700 0. 9 40/53 +/-4 (? ) 8. 2/5. 8 15 Nov 07 Fall 08 Units m. A mm cm cm nm nm (+/-) mrad x 100 32

Long Range PEP-II Upgrades • Over the next 4 years PEP-II will add: – – – – – Four RF stations Reduce by* 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, 2003 33

SLAC EPAC June 12, 2003 34

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 FY 2002 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-2 s-1. More machine studies will help. • Upgrades for Summer FY 2003 are on track. • There are long range plans leading towards L >2 x 1034 cm-2 s-1. SLAC EPAC June 12, 2003 35

Comparison of KEKB and PEP-II to date PEP-II KEKB SLAC EPAC June 12, 2003 36

PEP-II and KEKB Possible Luminosity Gains (estimated by J. Seeman June 2003) Effect PEP-II Gain KEKB Gain Lower by* 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) SLAC EPAC June 12, 2003 37

SLAC EPAC June 12, 2003 38

K. Oide’s Prediction of KEKB’s Integrated Luminosity SLAC EPAC June 12, 2003 39