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PEP- II Linac Accelerator Systems Department The PEP-II Overview John Seeman SLAC Particle and Particle-Astrophysics Directorate PEP-II MAC Review January 18, 2006
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PEP- II Linac Accelerator Systems Department Topics PEP-II brief status PEP-II future schedule PEP-II luminosity goals and projections PEP-II detailed upgrade plans
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PEP- II Linac Accelerator Systems Department The PEP-II Team August 2004
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PEP- II Linac Accelerator Systems Department PEP-II e + e - Collider Overview BaBar Detector
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PEP- II Linac Accelerator Systems Department The PEP-II e + e - asymmetric collider
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PEP- II Linac Accelerator Systems Department PEP-II RF Cavities
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PEP- II Linac Accelerator Systems Department PEP-II Interaction Region Components near BaBar HER LER Collision point BaBar
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PEP- II Linac Accelerator Systems Department How the beams enter and exit the PEP-II Interaction Region
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PEP- II Linac Accelerator Systems Department Two years ago before Trickle Injection Fill and coast is not efficient
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PEP- II Linac Accelerator Systems Department Present: Continuous Injection at PEP-II HER current LER current Luminosity
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PEP- II Linac Accelerator Systems Department PEP-II Highest Luminosity October 9, 2005 10 34
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PEP- II Linac Accelerator Systems Department
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PEP- II Linac Accelerator Systems Department 1 x 10 34 on October 9, 2005
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PEP- II Linac Accelerator Systems Department PEP-II Monthly Peak Luminosity 1 x10 34
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PEP- II Linac Accelerator Systems Department Run 5 AB
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PEP- II Linac Accelerator Systems Department
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PEP- II Linac Accelerator Systems Department Prediction July 2003 Actual
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PEP- II Linac Accelerator Systems Department Delayed start Summer weather Slope is good! Power outage Actual Prediction April 2005 LER BPM event Long down
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PEP- II Linac Accelerator Systems Department Recent Operation for Run 5b PEP-II turn-on (Run 5b) in mid-November. PEP-II operated through the holiday break. Luminosity ramped rapidly to 8.6 x 10 33. For the past month we have had three problems: –IR 6 HER vacuum leak –IR4 LER vacuum spikes and instability –IR2 LER/HER vacuum spikes and instability Several talks are dedicated to these issues.
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PEP- II Linac Accelerator Systems Department PEP-II Long Term Run Schedule Run 5a:April-September 2005 (done). Down: October 2005 (safety + small upgrades) Run 5b: November 2005-July 2006 Down: August-November 2006 (major upgrades for PEP-II & BaBar + LCLS installation) Run 6:December 2006-August 2007 Down:September-November 2007 (safety + LCLS installation) Run 7: December 2007-September 2008.
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PEP- II Linac Accelerator Systems Department Luminosity Equation for a Circular e + e - Collider y is the beam-beam parameter (~0.065) I b is the bunch current (1 to 3 mA) n is the number of bunches (~1700) y * is the IP lattice optics function (vertical beta) (10 mm) E is the beam energy (3.1 and 9 GeV) (fixed) Luminosity (10 33 cm -2 s -1 )
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PEP- II Linac Accelerator Systems Department PEP-II Overall Parameters and Goals ParameterUnitsDesign Present in collision 2007 goal I+mA214029504000 I-mA75017202200 Number bunches 16581732 y*y* mm15-20118-8.5 Bunch length mm1511-128.5-9 yy 0.030.044-0.0650.054-0.07 Luminosityx10 33 3.01020 Int lumi / day pb -1 1306621300 Five times designOver three times design
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PEP- II Linac Accelerator Systems Department Expected PEP-II Delivered Integrated Luminosity End of fiscal year Total PEP-II Projection Delivered Yearly change Running months each year Peak Luminosity x 10 33 FY2004256/fb117/fb109.2 FY2005311555.510 FY2006456145912 FY2007635179817.5 FY200810013661121 Projection December 2005
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PEP- II Linac Accelerator Systems Department Integrated Luminosity Projection Now December 2006 Run 5b Run 6 Run 7 Projection December 2006
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PEP- II Linac Accelerator Systems Department PEP-II Upgrades PEP-II luminosity has increased steadily over the past years due to carefully planned hardware upgrades and operational improvements. We are embarking on the next phase. The next factor of two in PEP-II luminosity (1 to 2 x10 34 /cm 2 /s) will come from: –Increasing each beam current by 40%. –Lowering y * from 11 to 8.5 mm giving 30%. –Increasing the beam-beam parameters by 10%. –Keeping detector backgrounds at the predicted levels. –Maintaining (and improving) accelerator reliability.
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PEP- II Linac Accelerator Systems Department Long Term Luminosity Projections
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PEP- II Linac Accelerator Systems Department PEP-II Limitations and How to Fix Them Categories of limitations and upgrades: –Hardware upgrades (AIP and OPS) –Operational issues –RF and longitudinal feedback –Transverse feedback –Lattice and optics –Beam-beam interaction –Reliability –Beam position monitors (BPMs) –Instrumentation –Machine-detector interface and backgrounds
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PEP- II Linac Accelerator Systems Department Task Force Approach Task forces have been addressing PEP-II issues for several years to deal with accelerator issues with the goal to provide more luminosity and higher integrated luminosity. We have started several new task forces this run to deal near-term and longer-term issues. All the task forces leaders meet on Wednesdays to provide a common focus and clear overall leadership. Each task force has identified key issues to address and has proposed machine studies, hardware improvements, and personnel changes. Machine studies are performed about twice each week. (Tuesday and Thursday day shifts) Accelerator improvement projects “AIP” are identified and started. Smaller hardware projects are addressed when identified and are funded by operations “OPS”.
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PEP- II Linac Accelerator Systems Department PEP-II Task Force Structure
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PEP- II Linac Accelerator Systems Department We appreciate contributions of outside groups! BaBar collaborators –USA members –Foreign members LBL accelerator and engineering staff Machine Advisory Committee (Chair: D. Rice) SLAC Accelerator Research staff ILC accelerator physicists SLAC support groups (engineering, software, …)
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PEP- II Linac Accelerator Systems Department Task Force Action Item List 1) RF:Fill all klystron sockets with working tubes and plan for future. 2) RF:Get LLRF working on all stations with no trips. 3) Dynamics:Get longitudinal beam motion stable at higher currents and no trips. 4) Dynamics:Get transverse beam motion stable at higher current with no trips. 5) Optics:Fix beta beats, dispersion, and coupling in LER. 6) Optics:Analyze chromatic solenoid compensation in the IR for LER. 7) Optics:Look for magnets (quadrupoles) with incorrect fields. 8) Steering:Find sources of orbit jitter and drift. Turn on Global Orbit Feedbacks. 9) Beam-Beam:Turn on the LER wiggler to half strength; then full strength. 10) Beam-Beam: Improve specific luminosity to >4.0 at high currents. 11) Beam-Beam:Lower horizontal tunes to closer to half integer. 12) Reliability:Account for downtime and beam tuning in a way that is better for PEP-II improvement. What are the major items to fix in advance. 13) BPM:Determine the BPM operating strategy for LER. New LER Arc BPM frequency or better analysis. 14) Instrumentation: New IP dither and better SLM analysis 15) MDI/ & Backgrounds: Improve the interface and backgrounds of PEP-II and BaBar
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PEP- II Linac Accelerator Systems Department Accelerator Physics Studies Needed for 2x10 34 Better understanding of beam-beam effects –Parasitic crossings –Small crossing angles –Higher tune shifts Reduce beam aborts –RF trips –Longitudinal instabilities –Transverse instabilities –Better backgrounds Better magnetic lattice optics –Lower y* –Reduce beats –Improve luminosity tuning knobs Increase LER emittance with wigglers Continue to improve HOM damping at higher currents Determine instability growth rates in LER/HER at high currents –Transverse –Longitudinal –Electron cloud –Fast positron transverse growth rate Machine-detector interface –Reduce backgrounds in trickle charge –Reduce IP pressure with current
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PEP- II Linac Accelerator Systems Department Accelerator Improvement Projects (AIP) X-Y BPM upgrades2005-2006 New HER Q5 vacuum chambers2005-2006 New HER/LER Q2 chambers2006 HER-10 RF station2006 HER-11 RF station2006 New transverse digital delay2005 HER power supply upgrade for higher tunes2006 LLRF comb-2 project2005-2006 New HER Q4 vacuum chambers2006 NEW IR2 Q2 bellows2006 LER IR HOM absorber2006 HER IR HOM absorber2006 Klystron linearizer2006 LER BPM monitor upgrade2006 LER new high power bellows2006 LER NEG vacuum chamber upgrade2006 New Longitudinal feedback processor2006 Cost of remaining AIP projects is about 8 M$ spread over two years. PEP-II AIP expenditures from 1999-2005 averaged about 5 M$ each year.
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PEP- II Linac Accelerator Systems Department Projects for Beam Current Increase ( L=40%) HER: (1.7 A 2.2 A) –AIP: HER-10 RF station 2006 –AIP: HER-11 RF station 2006 –AIP: HER Q5 vacuum chamber 2005 and 2006 –AIP: HER Q4 vacuum chamber 2006 –AIP: IR HOM absorber 2006 –OPS: Cooling water exchanger modifications 2005 –OPS: IR DS7 transition LER: (2.9 A 4 A) –AIP: IR HOM absorber 2006 –AIP: High power bellows 2006 –AIP: LER Q4 chambers –AIP: LER Q5 chambers –OPS: Abort window spoiler upgrade Both rings: –AIP: New transverse feedback digital delay 2005 –AIP: Low Level RF Comb-2 project 2005-2006 –AIP: Q2 vacuum chamber 2006 –AIP: IR2 Q2 high power bellows 2006 –AIP: Klystron linearizer 2006 –AIP: Longitudinal feedback processor 2006 –OPS: Increased thermal monitoring 2005-2006 –OPS: Feedback amplifier upgrades 2005-2006
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PEP- II Linac Accelerator Systems Department Example: PEP-II RF Cavities (Fall 2006) RF Cavities Each cavity: 850 kV 500 kW 476 MHz HOM loads Ceramic windows
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PEP- II Linac Accelerator Systems Department Klystrons and Power Supplies (Fall 2006) R. Cassel et alC. Pearson et al Klystron group to produce 7 klystrons in 14 months
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PEP- II Linac Accelerator Systems Department Example PEP-II kicker modules upgrades (Fall 2004+2005) Longitudinal Transverse Bunch-by-bunch feedbacks with 4 nsec spacing
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PEP- II Linac Accelerator Systems Department Many of the new vacuum chambers for higher current are near the IP Dots show new vacuum chamber locations. Done
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PEP- II Linac Accelerator Systems Department Example: HER QF5L Chamber (Fall 2005) Specifications Design Construction R. Pope
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PEP- II Linac Accelerator Systems Department Example: LER/HER Q2 IR Vacuum Chamber (Fall 2006) High power separation chamber Thermal analysis of synchrotron radiation power (~100 W/cm) NEG Vacuum Pump S. Metcalfe
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PEP- II Linac Accelerator Systems Department Example: HER Q4/5 Chambers (Fall 2006) Q5R BPM Q4R BPM 27.5 inches 14 inches e- Looking upbeam BPM Timing BPMs Electron BPMs
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PEP- II Linac Accelerator Systems Department Example: Q4/Q5 Bellows Layout (Fall 2006) N. Kurita
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PEP- II Linac Accelerator Systems Department Problem with LER Beam Position Monitor Units A situation with transverse offset bunches, high bunch currents and short length positron bunches caused a vacuum failure in a BPM in June 2005. The problem is systemic. We have carefully analyzed the situation.
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PEP- II Linac Accelerator Systems Department Analysis of BPM thermal properties and RF modes has been carried out Old design Likely new design Kurita Ng Novokhatski Smith Johnson Feed through BPM button Connector
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PEP- II Linac Accelerator Systems Department BPM Heating Model and Fix x x S. Ecklund damaged BPM present We have a numerical model (Ecklund) of BPM heating including bunch charges, bunch lengths (RF voltage), and transverse position offsets. We can now reasonably predict when a problem will occur. Upgrade plan for Fall 2006: Repair LER Arc BPMs (~200), IR2 BPMs need to be modified (~50), but the straight section BPMs are ok (~80). Add thermo- couples to many BPMs. Then we can go to short bunches and 4 A. Planned fix: arb. units Bunch lengthening
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PEP- II Linac Accelerator Systems Department Lower y * from 11 to 8.5 mm ( L=30%) HER –OPS: Raise RF voltage from 14 MV to 18 MV. –AIP: HER-10 RF station –AIP: HER-11 RF station –OPS: Install several SLAC klystrons to replace aging klystrons for more power. –AIP: HER power supply upgrade for higher tunes 2006 ( lower momentum compaction) –OPS: Lattice optics correction in the IR LER –Raise RF voltage from 4 MV to 6.4 MV. –AIP: LER BPM monitor upgrade (2006). –OPS: Install several SLAC klystrons to replace aging klystrons for more power. –OPS: Lattice optics corrections in the IR
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PEP- II Linac Accelerator Systems Department Lattice-Optics Work Improve Orbit Response Matrix (ORM) tool Improve Model Independent Analysis (MIA) model Continue beam-based alignment (BBA) Improve on-line optic models Develop improved interaction region adjustment ‘knobs’ Begin daily comparisons of model and real tunes Improve model versus measurement agreement Tenenbaum, Wienands, Wittmer, Cai
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PEP- II Linac Accelerator Systems Department Raising the Beam-Beam Parameters ( L=10%) HER: –OPS: Arc and IP orbit, coupling, dispersion corrections ongoing LER: –OPS: Arc BPM conversion 952 to 476 MHz processors 2006 (tbd) –AIP: Arc and IP orbit, coupling, dispersion corrections ongoing Both rings: –AIP: X-Y BPM conversion 2005-2006 –OPS: Improve higher specific luminosity with IP lattice adjustments –OPS: Lower horizontal tune closer to half integer ongoing –OPS: Global Orbit Feedbacks (GOF) re-commissioned 2005 –OPS: Run additional beam-beam simulations finding better beam parameters.
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PEP- II Linac Accelerator Systems Department Beam-Beam Simulations Y. Cai U. Wienands K. Sonnad Luminosity beam-beam simulations agree with present beam conditions. Simulations done for future beam conditions agree well with spread sheet estimates. Studies will continue.
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PEP- II Linac Accelerator Systems Department PEP-II Beam-Beam Simulations Full strong-strong simulations with full bunch currents, parasitic collisions, and full EM fields are tracked to equilibrium. L > 2 x 10 34
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PEP- II Linac Accelerator Systems Department PEP-II Conclusions PEP-II turn-on in Run 5 is going well (in spite of the power outage and summer heat). In October achieved a new luminosity record (1x10 34 ) PEP-II has delivered ~333 fb -1 since May 1999. Recent instabilities are being addressed. Trickle injection in both rings all of the time. Run time is up. Planned upgrades towards >2 10 34 are on track. Accelerator issues with PEP-II are being studied. Task Forces are under way to address these accelerator issues A run plan is in place with a target of 1 ab -1 in 2008.
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