1 / 57

PEP-II Status

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…. Run 4 Synopsis.

ehagerman
Télécharger la présentation

PEP-II Status

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. 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

  3. 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

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

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

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

  7. 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

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

  9. 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

  10. 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

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

  12. 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

  13. HER Trickle Charge • 1st test in Feb. 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

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

  15. 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

  16. HER Steering • Steer the HER “flat” except for IR 2 • 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

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

  18. 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. HER ßy* Reduction We used 60% of a knob designed to bring ß* down to 10 mm Significant tuning work required post-STDZ to regain luminosity benefit U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

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

  20. 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

  21. 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

  22. 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

  23. 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

  24. PEP Fill Patterns 1415 bunches trains of 15, 4.2 ns 1550 bunches trains of 33, 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

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

  26. 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

  27. 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

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

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

  30. 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

  31. 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

  32. 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/dayincl. l. inst. 3.7/day PEP Rf Beam Aborts Run 3 Run 4 Despite the overall improvement, # rf trips actually increased significantly after Dec. 03 U. Wienands, SLAC-PEP-II PEP MAC, 15…17-Apr-04

  33. 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

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

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

  36. 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

  37. 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

  38. 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

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

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

  41. 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

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

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

  44. Multibunch Stability • Grow-damp measurements • 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

  45. 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

  46. 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

  47. 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

  48. 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

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

  50. Rf Improvements • New PowerPC IOC processors • 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

More Related