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Accelerator R&D Results from the B-factory

Accelerator R&D Results from the B-factory. M. Sullivan PEP-II run coordinator. Outline. PEP-II Parameters Vacuum designs RF systems Bunch by bunch feedbacks High-current running Synchrotron radiation power HOM power IR design SuperB IR design Summary. PEP-II Rings. BaBar Detector.

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Accelerator R&D Results from the B-factory

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  1. Accelerator R&D Results from the B-factory M. Sullivan PEP-II run coordinator

  2. Outline • PEP-II Parameters • Vacuum designs • RF systems • Bunch by bunch feedbacks • High-current running • Synchrotron radiation power • HOM power • IR design • SuperB IR design • Summary

  3. PEP-II Rings BaBar Detector

  4. PEP-II tunnel

  5. PEP-II parameters Circumference (m) 2200 RF frequency (MHz) 456 Number of RF buckets 3492 Number of bunches 1730 Bunch spacing (m) 1.26 LERHER Beam current (A) 2.9 (2.99) 1.85 (1.9) Particles per bunch 81010 51010 Beam energy (GeV) 3.1 9 Collision beam sizes (m) 100x5 Collision Head-on Luminosity (cm-2 sec-1) 1.21034 Highest beam currents and more positrons than anyone else

  6. Vacuum Systems • HER • Long (5.4 m) PEP-I dipoles led to distributed ion pumps (DIPS) • Copper system • LER • Short (0.45 m) dipoles to decrease the damping time led to ante-chambers with photon stops and massive titanium sublimation pumps (TSPs) • Aluminum system (TiN) • Base pressures are less than a nTorr • Dynamic pressures are a few nTorr • More Amp-hours than any other accelerator • Over 50,000 Amp-hrs for the LER • Over 30,000 Amp-hrs for the HER

  7. RF System and Feedbacks • RF systems • Minimal stored energy • Power efficient • Beam loading is high • State of the art low-level feedback system to control klystron power and phase • Fast feedback systems to control multi-bunch instabilities in the transverse and longitudinal dimensions • Longitudinal system has been installed in several other storage rings

  8. High Beam Currents • Synchrotron Radiation power • 6.4 MW for the HER at 1.8 A • 2.3 MW for the LER at 3 A • HOM power • Absorbing elements • Pump screens • Bellows screens • Ion gap • Gap is now 1% -- ions have only seen when the vacuum is high • Electron cloud • Successfully controlled by solenoid windings

  9. HOM power damage RF seal between two flanges in the HER

  10. Absorber designs S. Weathersby A. Novokhatski

  11. Design for a HOM Absorber Module

  12. Bellows Design with Exposed Tiles

  13. New Absorber Design Absorber tiles are now behind the bellows fingers and the spacing between the fingers is quite large to allow high frequency RF to pass through

  14. IR Design • Uses permanent magnets for accelerator components inside the detector magnetic field • Require no power • Are always on – reduces the probability that an uncontrolled beam will crash into the detector • Maintenance free • Self-shielding

  15. e+ e- PEP-II Interaction Region BaBar Detector

  16. IR Layout

  17. Super B Factory • Worked on an interaction region design for a Super B Factory • The design incorporates super-conducting elements as well as permanent magnet elements for the final focus optics • Similar beam currents and storage ring sizes as PEP-II • Ring optics, HOM issues, beam stability… • Trickle injection – pioneered at PEP-II and KEKB is a crucial ingredient for any future high-current collider • About one FTE at SLAC works on the SuperB to support the world wide effort . Not directed to any one particular site yet…

  18. Super B Interaction Region

  19. SuperB IR Closeup

  20. Summary • PEP-II is a working accelerator with high-current rings • Many of the issues for the ILC damping rings have been or can be studied at PEP-II • Over 100 accelerator papers have been written about PEP-II with regard to the high-current performance • As we increase beam currents, PEP-II will move further into the frontier of high-current storage rings

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