PEP- II Linac Accelerator Systems Department
The PEP-II Overview
John SeemanSLAC Particle and Particle-Astrophysics Directorate
PEP-II MAC ReviewJanuary 18, 2006
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
PEP- II Linac Accelerator Systems Department
The PEP-II Team
•
August 2004
PEP- II Linac Accelerator Systems Department
PEP-II e+e- Collider Overview•
BaBarDetector
PEP- II Linac Accelerator Systems Department
The PEP-II e+e- asymmetric collider
PEP- II Linac Accelerator Systems Department
PEP-II RF Cavities
PEP- II Linac Accelerator Systems Department
PEP-II Interaction Region Components near BaBar
HER
LER
Collision point
BaBar
PEP- II Linac Accelerator Systems Department
How the beams enter and exit the PEP-II Interaction Region
PEP- II Linac Accelerator Systems Department
Two years ago before Trickle Injection
•
Fill and coastis not efficient
PEP- II Linac Accelerator Systems Department
Present: Continuous Injection at PEP-II
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HER current
LER current
Luminosity
PEP- II Linac Accelerator Systems Department
PEP-II Highest Luminosity October 9, 2005
•
1034
PEP- II Linac Accelerator Systems Department
•
PEP- II Linac Accelerator Systems Department
1 x 1034 on October 9, 2005
•
PEP- II Linac Accelerator Systems Department
PEP-II Monthly Peak Luminosity
• 1 x1034
PEP- II Linac Accelerator Systems Department
•
Run 5A B
PEP- II Linac Accelerator Systems Department
•
PEP- II Linac Accelerator Systems Department
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Prediction July 2003
Actual
PEP- II Linac Accelerator Systems Department
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Delayed start
Summer weather
Slope is good!
Power outage
Actual
Prediction April 2005
LER BPM event
Long down
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 1033.• 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.
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.
PEP- II Linac Accelerator Systems Department
Luminosity Equation for a Circular e+e- Collider
y is the beam-beam parameter (~0.065)
Ib 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 (1033 cm-2 s-1)
*341017.2
y
byEInxL
PEP- II Linac Accelerator Systems Department
PEP-II Overall Parameters and Goals
Parameter Units DesignPresent in collision
2007 goal
I+ mA 2140 2950 4000
I- mA 750 1720 2200
Number bunches
1658 1732 1732
y* mm 15-20 11 8-8.5
Bunch length mm 15 11-12 8.5-9
y 0.03 0.044-0.065 0.054-0.07
Luminosity x1033 3.0 10 20
Int lumi / day
pb-1 130 662 1300
Five times designOver three times design
PEP- II Linac Accelerator Systems Department
Expected PEP-II Delivered Integrated Luminosity
End of fiscal yearTotal PEP-II Projection
Delivered
Yearly change
Running
months
each year
Peak
Luminosity
x 1033
FY2004 256/fb 117/fb 10 9.2
FY2005 311 55 5.5 10
FY2006 456 145 9 12
FY2007 635 179 8 17.5
FY2008 1001 366 11 21
Projection December 2005
PEP- II Linac Accelerator Systems Department
Integrated Luminosity Projection
NowNow
December 2006
Run 5b
Run 6
Run 7
Projection December 2006
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 x1034/cm2/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.
PEP- II Linac Accelerator Systems Department
Long Term Luminosity Projections
•
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
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”.
PEP- II Linac Accelerator Systems Department
PEP-II Task Force Structure
•
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, …)
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
PEP- II Linac Accelerator Systems Department
Accelerator Physics Studies Needed for 2x1034
• 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
PEP- II Linac Accelerator Systems Department
Accelerator Improvement Projects (AIP)• X-Y BPM upgrades 2005-2006• New HER Q5 vacuum chambers 2005-2006• New HER/LER Q2 chambers 2006• HER-10 RF station 2006• HER-11 RF station 2006• New transverse digital delay 2005• HER power supply upgrade for higher tunes 2006• LLRF comb-2 project 2005-2006• New HER Q4 vacuum chambers 2006• NEW IR2 Q2 bellows 2006• LER IR HOM absorber 2006• HER IR HOM absorber 2006• Klystron linearizer 2006• LER BPM monitor upgrade 2006• LER new high power bellows 2006• LER NEG vacuum chamber upgrade 2006• New Longitudinal feedback processor 2006
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.
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
PEP- II Linac Accelerator Systems Department
Example: PEP-II RF Cavities (Fall 2006)
RF Cavities
Each cavity:850 kV500 kW476 MHzHOM loadsCeramicwindows
PEP- II Linac Accelerator Systems Department
Klystrons and Power Supplies (Fall 2006)
•
R. Cassel et alC. Pearson et alKlystron group to produce 7 klystrons in 14 months
PEP- II Linac Accelerator Systems Department
Example PEP-II kicker modules upgrades (Fall 2004+2005)
Longitudinal
TransverseBunch-by-bunch feedbacks with 4 nsec spacing
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
PEP- II Linac Accelerator Systems Department
Example: HER QF5L Chamber (Fall 2005)
Specifications
Design
ConstructionR. Pope
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
PEP- II Linac Accelerator Systems Department
Example: HER Q4/5 Chambers (Fall 2006)
•
Q5R BPMQ4R BPM
27.5 inches14 inches
e-e-
Looking upbeam
BPM Timing BPMs
Electron BPMs
Electron BPMs
Electron BPMs
PEP- II Linac Accelerator Systems Department
Example: Q4/Q5 Bellows Layout (Fall 2006)Example: Q4/Q5 Bellows Layout (Fall 2006)
• N. Kurita
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.
PEP- II Linac Accelerator Systems Department
Analysis of BPM thermal properties and RF modes has been carried out
• Old design
Likely new design
KuritaNgNovokhatskiSmithJohnsonFeed through
BPM button
Connector
PEP- II Linac Accelerator Systems Department
BPM Heating Model and Fix
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 0.5 1 1.5 2 2.5 3 3.5
ib
2.5
3
3.5
4.05
4.5
5
5.4
6
6.5
Relative Power vs. bunch current for 1740 bunches
Vrf
x
x
S. EcklundS. Ecklund
damagedBPMdamagedBPM
presentpresent
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 whena problem will occur.
Upgrade plan for Fall 2006:Repair LER Arc BPMs (~200), IR2 BPMs need to bemodified (~50), but the straight sectionBPMs 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
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
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
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.
PEP- II Linac Accelerator Systems Department
Beam-Beam Simulations•
Y. CaiU. WienandsK. 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.
PEP- II Linac Accelerator Systems Department
PEP-II Beam-Beam Simulations
•
Full strong-strong simulationswith full bunch currents,parasitic collisions, and full EM fields aretracked to equilibrium.
L > 2 x 1034
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 (1x1034)
• 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 >21034 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.