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Super-B Accelerator Overview

Super-B Accelerator Overview. John Seeman for the Super-B Study Group PPA Directorate Stanford Linear Accelerator Center Super-B Detector R&D Workshop February 14-16, 2008. Topics. Super-B design Polarization of e- Daphne status KEK-B Crab cavity studies. Accelerator status.

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Super-B Accelerator Overview

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  1. Super-B Accelerator Overview John Seeman for the Super-B Study Group PPA Directorate Stanford Linear Accelerator Center Super-B Detector R&D Workshop February 14-16, 2008

  2. Topics • Super-B design • Polarization of e- • Daphne status • KEK-B Crab cavity studies

  3. Accelerator status • SBF accelerator layout has converged and been defined. • Site constraints suggest 1650 m + polarization component length for a total of 1800 m. • A luminosity of 1x1036 with longitudinal polarization of one beam at the interaction point is the primary goal. • Overall parameters have a x4 luminosity growth potential to the 4x1036 level. • Many of the systems use existing components or component designs. • Interaction region has new features. Most of the future design work will be concentrated there.

  4. Possible site in the Tor Vergata University close to the Frascati Lab M. Sullivan

  5. Super-B Territory • The Tor Vergata campus area is owned by the University • The building code allows development with limited bureaucratic complexity (within reason): • limit number and extension of buildings • no shacks or barracks • distance from Roman Villa archeological area • possible archeological issue with access shafts • Geology is good • Terrain is geologically stable (pozzolanic ash and then tuff) • Water is at about -50m, no interference with tunnels • Need extensive geological samples to evaluate local stability • Micro seismic data are not available at this time • tunnel depth between 10 and 30m

  6. 3 km

  7. 100m Footprint SuperB Ring (about 1800m) SPARX SuperB Injector (about 400m) Roman Villa SuperB Main Building

  8. Super-B Tunnels • Tunnel boring machine available with 6.70m external diameter. Internal diameter a bit less than 5.80m. • Linac will need a double tunnel for the RF and klystrons • Main ring will use a single tunnel with 4 or 6 surface service buildings Division not necessarily useful.

  9. Total length ~1800 m Length 20 m Length 280 m November 2007 layout Courtesy E.Paoloni, G. Marchiori

  10. SuperB Parameters (Nov. 2007) (In red the CDR values)

  11. Rings optical functions LER HER

  12. x-plane xmax = 60 sx no coupling y-plane ymax = 30 sy full coupling Dynamic Aperture With crab sextupoles • DA represents stability area • of particles over many turns • Lifetimes depend on it Crab sextupoles reduce DA by 30%

  13. Basic concepts

  14. x bY e- e+ Vertical waist has to be a function of x: Z=0 for particles at –sx(- sx/2q at low current) Z= sx/q for particles at + sx(sx/2q at low current) Crab waist realized with 2 sextupoles in phase with the IP in X and at p/2 in Y 2Sx/q q 2Sz*q z 2Sz 2Sx Crab waist removes bb betratron coupling Introduced by the crossing angle

  15. Beams are focused in the vertical plane 100 times more than in the present factories, thanks to: - small emittances - small beta functions - large crossing angle - Crab waist Tune shifts and longitudinal overlap greatly reduced KEKB Beams distributions at the IP SuperB Beams distributions at the IP

  16. Crab sextupoles Final Focus optical functions LER:bx* = 35 mm, by* = 220 m HER:bx* = 20 mm, by* = 390 m

  17. Accelerator parameters [4x1036 parameters] LER HER Energy (GeV) 4.0 7.0 Current (A) 3.69 3.69 No. bunches 2502 Bunch spacing (m) 0.63 Beta x* (mm) 20 20 Beta y* (mm) 0.2 0.2 Emittance x (nm-rad) 1.6 1.6 Emittance y (pm-rad) 4 4 Full crossing angle (mrad) 34 These parameters constrain or define the IR design M. Sullivan

  18. SR Power Numbers The total power is similar to PEP-II SR power in QD0 (kW) for beam currents of 1.44A HER and 2.5A LER No QD0 offsets SuperB PEP-II 3A on 1.8A Incoming HER 41 4 49 Incoming LER 28 1 16 Outgoing HER 41 93 49 Outgoing LER 28 55 16 Total 138 153 130

  19. “Foot print” shape preferred

  20. IP Spin Rotator layout

  21. Polarization Components from the SLC at SLAC Example of Injected Polarized Electrons Polarized Photo-Gun 120 Hz, 87% 2 x 5x10^10/pulse Spin manipulators SLC IP Located at the Stanford Linear Accelerator Center Polarization equipment ready for reuse!

  22. Polarization Comments • Long polarization times and short beam lifetimes indicates a need to continuously inject polarized electrons in the vertical plane. • There are several possible IP spin rotators. • Solenoids look better at present. • Expected longitudinal polarization at the IP of about 87%(inj) x 97%(ring)=85%(effective).

  23. PEP-II Arc Section Usable PEP-II components for Super-B Magnets (Over 1500) Vacuum chambers (4400 m) RF systems (15 stations, 28 cavities) Power supplies Bunch-by-bunch feedback systems Diagnostics Instruments Injection septa and kickers Supports

  24. B-Factory RF Klystrons and Cavities

  25. Where to go from here for Super-B? • Complete next round of studies for: • Updated design document. • Dynamic aperture studies. • Vibration and stability tolerances. • IR layout (+/- 50 m) • Injection conditions • Polarization rotation hardware

  26. Raimondi: Status of Crab Waist Studies at Daphne (Frascati) • Installation of the crab-waist IR finished in November 2007. • Present currents: 950 mA e- x 400 mA e+ • Ring optics (betas) are well matched (<5%). • Betas y/x = 9 mm/0.25 m  6-7 mm/0.25 m after detector is installed. • X-Y coupling ~0.6% • Collisions are well established. • Crab sextupoles are successfully tested to 40% value with beam. • Ring impedance better (40% lower). • e- instabilities threshold up by x2. • e+ instability threshold down by x2. • Luminosity looks ok but needs to be cross checked. • Run until ~end July. • Overall the situation looks good! (February 7, 2008)

  27. KEKB MAC: Status of KEKB Crab Cavity Studies • Crab cavities work well. • Beam “crabs” properly all around the ring. • At low current the specific luminosity is higher as predicted (geometric gain). • At high current some beam-beam force removes the gain in specific luminosity. • At high currents the beam lifetimes are reduced. • Studies have been going on for a year and will likely continue for the next year. (December 2007)

  28. Crab RF system

  29. Crab cavities in the KEKB tunnel HER LER

  30. Overview of crab cavity operation High-current High-current Physics run with Crab Low-current collision tuning Low-current collision tuning Summer shut down Warm up to room temperature

  31. Specific Luminosity L18 H24 (3/11, 4/3) L18 H24 (4/10, 4/19) y~0.089 L24 H24 (3/29, 4/1) L24 H29 (6/14) 22mrad crossing L18 H24

  32. beam-beam simulation (IbL/IbH = 7/4) y~0.089

  33. Beam-beam parameter with crab crossing (simulation) beam-beam parameter : experiments

  34. Machine Parameters (Nov. 28 2007) This is almost equal to the value achieved at collision with longer bunch spacing. Effects of high current and short spacing are not so big?

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