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

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

PEP-II Rings BaBar Detector 3

PEP-II tunnel 4

PEP-II parameters Circumference (m) 2200 RF frequency (MHz) 456 Number of RF buckets 3492 Number of bunches 1730 Bunch spacing (m) 1.26 LER HER 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 5

Vacuum Systems HER LER Base pressures are less than a nTorr 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 6

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 7

High Beam Currents Synchrotron Radiation power HOM power Ion gap 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 8

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

Absorber designs S. Weathersby A. Novokhatski 10

Design for a HOM Absorber Module 11

Bellows Design with Exposed Tiles 12

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 13

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 14

PEP-II Interaction Region BaBar Detector 15

IR Layout 16

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… 17

Super B Interaction Region 18

SuperB IR Closeup 19

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 20