U. Wienands, PEP-II Run Coordinator …for the PEP-II team PEP-II Status U. Wienands, PEP-II Run Coordinator …for the PEP-II team

Outline of Talk Run 4 Synopsis Machine tuning & improvements Issues encountered during Run 4 Other improvements and MD items Outlook: the remainder of Run 4… U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Run 4 Synopsis PEP is now delivering twice the rate of Run 3 Over 60/fb delivered in Run 4, over 200/fb tot Key ingredients: trickle-charge both rings Raise peak Lumi to 8.34E33 (currents, ß*, orbit) Aggressively track down & reduce rf trips. MD program focused on near-term improvements + strategic studies needed for upgrades. U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Run 4 Delivered Luminosity U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Running 7-day Integral (2004) U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Run Time Accounting, Run 4 BaBar up from ≈56% to 60% Tuning/Fill down from ≈22% to 20% Downtime down from 16…19% to 14% U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Machine Tuning and Improvements LER & HER trickle charge Steering of the HER Lowering ßy* of the HER (12–>11 mm) Raising of the HER rf voltage Raising the number of bunches & beam currents U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER Trickle Charge PEP issues mostly resolved last fall BIC, diagnostics software Extended BaBar trickle test late Oct. 03 followed by analysis of data quality Trickle in production beginning Dec. 2,03 Daily luminosity up from 250 to 350/pb ≈15% is direct trickle gain, remainder is increased efficiency (less trips) Dec. a particularly stable month for rf. U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER only Trickle Day U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER Trickle Background Monitor FFT of Injection- triggers (s harmonics if off energy) Injection-generated triggers (∫ also avail. as EPICS PV) U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

HER Trickle Charge 1st test in Feb. 04 2nd test mid-March 04 significant reduction in injection background not at full beam current, high radiation spikes 2nd test mid-March 04 Radiation spikes no longer an issue due to cleanup work in injector Break-even luminosity reached. BaBar state machine now ready for double trickle Double-trickling operationally since March 11. U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Double-Trickle Gain LER-only trickle av-to-pk = 87% Double trickle av-to-pk = 99% => 12% gain U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Almost Best Day of PEP-II The best day actually had 669/pb delivered. U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

HER Steering Steer the HER “flat” except for IR 2 Motivation this has worked historically IR 2 steering in the past has caused difficulties with coupling Motivation lower vertical dispersion better acceptance better agreement of the lattice with the design U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Orbit (absolute) Y dispersion Coupling (C12,n) ßx/ßx,design U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

We used 60% of a knob designed to bring ß* down to 10 mm HER ßy* Reduction We used 60% of a knob designed to bring ß* down to 10 mm Before ßy* reduction ßy* ≈ 12.3 mm ßx* ≈ 28 cm Benefit for luminosity HER beam “stronger” 3% increase in spec. lumi. Before STDZ After ßy* reduction ßy* ≈ 11.0 mm ßx* ≈ 27 cm After STDZ ßy* ≈ 10 mm ßx* ≈ 25 cm ßx* lower due to larger global ßx beat. Significant tuning work required post-STDZ to regain luminosity benefit U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Coupling after ßy* Reduction U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Lowering HER ßy* (cont’d) To be able to meaningfully reduce ßy*, we are raising the HER rf voltage. At 18 MV we expect 11 mm bunch length. The rate of rise is limited by increased rf trip rate. U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Fill Patterns & Beam Currents At the beam-beam limit need to raise # bunches and beam current to gain lumi. Need to run by-2 (4.2 ns) bunch spacing: How will electron-cloud effects behave? Will luminosity scale with # bunches? What is the effect of parasitic crossings? How will HOM heating behave? (only the last expected to be better) U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Raising # Bunches & Beam Currents Bunch currents: ≈ 1.5 mA (LER) ≈ 0.9 mA (HER) fairly constant U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Spec. Luminosity vs # Bunches Fixed bunch current in both rings Fixed by-2 pattern with mini trains Vary train length, thus # of bunches U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

PEP Fill Patterns 1415 bunches trains of 15, 4.2 ns Note: 1st and last bunch have lower luminosity: only one parasitic xing “Pilot bunches” (no parasitics) have even less luminosity! U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Luminosity vs IHER*ILER U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Issues encountered IR 2 vacuum and background issues Rf issues LER orbit & beam optics issues Bunch-by-bunch feedback issues U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

The IR 2 Vacuum Problem Late March, we regn’d the IR 2 NEGs Pressure and background had been on rise At Run 4 startup, NEGs regen’d before 1st beam After this, LER backgrounds and pressures much worse than before Also, long time constants (≈hours) observed Strongly bunch-length dependent Scrubbing very slow, almost 2 weeks NEGs being heated by HOMs to several 100°F U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER Vac. Gauge close to IR U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER Vacuum Pump @ -28 m U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

NEG Temperature at -28 m In essence, the NEG is being constantly regen’d with beam! U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Rf Issues Rf has been holding up better than in Run 3 thanks to significant effort of the RFTF The primary issues/causes of trips endemic failure (again) of SCRs in the HVPS phase drifts (esp. LER 4-5) & other board issues various tuner issues klystron issues misc. IOC issues U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

PEP Rf Beam Aborts Run 3 Run 4 HER rf trips: 5.0/day LER rf trips: 2.0/day Total: 7.0/day HER rf trips: 2.1/day LER rf trips: 0.9/day Total: 2.3/day incl. l. inst. 3.7/day Despite the overall improvement, # rf trips actually increased significantly after Dec. 03 U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER Orbit Issues Steer the ring without the IR, as has worked before. LER IR steering perilous due to BPM offsets This caused a large drop in spec. luminosity Root cause was a large beat in ßx, also, dispersion still >50 mm rms. No obvious quick fix => backed out Presently using MIA to try finding a correction strategy. U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER Steered Orbit U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER ßx after Steering U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Other improvements and MD BPM improvements Modeling improvements (incl. ORM, C12) Transverse grow-damp measurements Longitudinal grow-damp measurements New RF 8-1 klystron New rf IOCs using PowerPC controllers Injection Crossing-angle experiment U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

BPM Improvements BBA on all possible IR 2 BPM/quad pairs Offsets from this BBA now in DB Auto-calibration every 8 hours after a beam-dump Timing database updated New procedure to measure timing during delivery See talks by Smith & Ross U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Online Model Improvements Updated online models for both rings Survey data for IR 2 elements More accurate parametrization of QD1 Can run a model against machine config. & orbit Model runs on pepoptics => can use MAD & new version of DIMAD. C12 coupling analysis now online U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

HER Model vs Measurement(y) U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

History of ß Functions at the IP U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Orbit-Response Measurements ORM (LOCO) running on pepoptics HER and LER data taken ß function analysis consistent with phase-advance analysis More work needed to understand quad-strength factors => presentation by C. Steier U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

HER ORM ß/ßdesign U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

HER ORM – Magnet strengths Relative to design strengths. E(HER) = 8.9732 GeV U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Multibunch Stability Grow-damp measurements HER transverse: HER: longitudinal & transverse HER transverse: good margin in x, strong nonlinearity in y, longitudinal: only 20…30% margin for low-lying long. modes Low-group-delay Woofer significantly better. As a result of the HER measurements, we raised priority on the new Woofer U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

HER TFB Damping (x) HER X damping Data suggest stability up to 2…3 A beam current by-2 fill pattern. U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Crossing Angle Experiment Xing angle or not for the IR upgrade in 2005? Measurements done: Sensitivity of ∑x to beam-beam Sensitivity of Lumi to xing angle vs currents Results: L vs x separation becomes narrow at high I L vs x’ becomes somewhat narrower at high I U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Xing Angle Expt: Lum. vs ∂X Simulation by I. Narsky using 3-d code by Y. Cai U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Injection Orbit Feedbacks With both rings trickling injection problems are highly visible. We are implementing feedback systems to stabilize the beams LER injecting beam now working, HER to follow requires BPM hardware changes Ring-orbit stabilization under development tricky because of modeling issues (Note: we do not let the GOFs steer at injection) U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

LER Injection Orbit Feedback U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Rf Improvements New PowerPC IOC processors New LLRF boards Old 68k units above 80% CPU load, causing stalls New LLRF boards New SLAC klystron for HER 8-1 U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

New SLAC Klystron in 8-1 U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Outlook: The remainder of Run 4 Lattice improvements Further ßy* reduction in both rings Complete LER steering (MIA work) Fix HER ßx beat Beam-current increases U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

ß* Limits Bunch lengths –> 1 cm ßy* ≤ 1 cm feasible & meaningful LER: 3.8 MV (achieved) HER: 18 MV (tough!) ßy* ≤ 1 cm feasible & meaningful tested knobs exist for both rings Lowering ßx* ?? not meaningful if beam-beam limited in both planes Maintain matched beam sizes U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Global Ring Issues Knob to reduce global HER ßx beat exists good in 1st order but beam life time reduced need to investigate higher-order effects Correction of global ßx beat in steered LER 1st MIA solution has some very strong quad changes => may be problematic in practice source of ß beat not yet clearly identified U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Beam current limits HER LER Rf power limit: ≥ 1600 mA Stability: ≈1400 at present, ≥1600 mA with new woofer LER Tested up to 2400 mA, likely higher limit with llrf tuning rf power limit ≈ 3000 mA thermal issues with TFB, LFB kickers U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

July 2004 Parameters (Goal) HER LER I (mA) 1450 2500 nbunches 1600 ßy* (cm) 1 x .035 .094 y .047 .07 Vrf (MV) 18 4 Lum (cm-2s-1) U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

Acknowledgments The work reported on in this talk has been done by many, in particular: F.-J. Decker, A. Fisher, R. Iverson, W. Kozanecki, S. Novokhatski, M. Ross, J. Seeman, M. Stanek, M. Sullivan, P. Tenenbaum, D. Teytelman, M. Woodley, G. Wormser, G. Yocky U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04