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Status on an IR Design for a Super-B Factory

Status on an IR Design for a Super-B Factory. M. Sullivan for the Super-B Factory Workshop Hawaii April 20-23, 2005. Outline. General B-factory parameters IR parameters Synchrotron Radiation Issues Present IR design Summary and conclusions. PEP-III Super B parameters

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Status on an IR Design for a Super-B Factory

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  1. Status on an IR Design for a Super-B Factory M. Sullivan for the Super-B Factory Workshop Hawaii April 20-23, 2005

  2. Outline • General B-factory parameters • IR parameters • Synchrotron Radiation Issues • Present IR design • Summary and conclusions

  3. PEP-III Super B parameters for a 11036 Luminosity Super B LER energy 3.5 GeV HER energy 8.0 GeV LER current 23.0 A HER current 10.1 A y*1.5 mm x* 15 cm X emittance 40 nm-rad Estimated sy* 1.7 mm Bunch spacing 0.315 m Number of bunches 6900 Collision angle 14 mrads Beam pipe radius 2.5 cm Luminosity 11036 cm-2 sec-1

  4. IR design parameters • Detector acceptance down to 300 mrad angle – forward and backward • Beam pipe radius of 2.5 cm • Translates to ±10 cm of active beam pipe • The Q2 septum is at 2.5 m

  5. SR constraints and limits… • PEP-II IR design ended up with ~10 /crossing– which is 2.39 Ghz– rate on the detector beam pipe (11 krad/yr) • Background levels from SR can be no more than factor of 100 to 1000 times higher than PEP-II before radiation doses get too high (occupancy may be OK for pixelated detector) • Make all of the SR radiation from local bends in the beam miss nearby surfaces (power from the high current beams is too high for local absorption)

  6. Current baseline design

  7. SR backgrounds photons > 4keV on the physics window beampipe Version  /X  /s Watts PEP-II design 10 2.39e9 1.4e-5 11 krad/yr Baseline design HER 4.65e4 4.37e13 0.86 LER 5.71e4 5.37e13 0.01 Offset Q4 10 mm & offset Q2 12 mm HER 141 1.33e11 3.1e-4 LER 244 2.29e11 1.1e-3 8 instead of 10 HER 140 1.32e11 2.8e-4 Tail #1 HER 5.8 5.45e9 1.3e-5 LER 9.6 9.03e9 4.2e-5 Tail#2 HER 0.10 9.40e7 2.2e-7 LER 0.15 1.41e8 6.8e-7 No tails HER 6.9e-14 6.49e-5 1.5e-19 LER 1.3e-11 0.012 6.9e-17

  8. Vertical plane is not as hard Horizontal plane is more difficult so try to steer the Q5 radiation away from the beam pipe

  9. Bending power vs quadrupole power Magnet Bending pwr Quadrupole pwr HER beam (10A) Up Q5 0 1672 W Up Q4 12800 W ~3000 W LER beam (23 A) Up Q2 3433 W 46 W

  10. What is the correct beam tail distribution? • The present PEP-II design is insensitive to the tail distribution since the SR background is dominated by local bending fans. This allowed us to assume a conservative (high) tail particle density • The PEP SuperB design minimizes local beam bending and hence the beam tail distribution becomes more important • Note: the background from SR comes only from the x plane

  11. Summary and Conclusions We have made progress on a PEP SuperB interaction region design with a luminosity of 11036 Synchrotron radiation backgrounds look managable. Much more work needs to be done…. Minimal beam bending leads to a design that is sensitive to the beam tail distributions, … Perhaps we can learn more about the correct beam tail distributions from the present B factories.

  12. Backup slides

  13. KEKB Upgrade Plans • Now UpgradesSuperKEKB • LER energy 3.5 3.5 3.5 GeV • HER energy 8.0 8.0 8.0 GeV • LER current 1.382.09.4 A • HER current 1.051.14.1 A • y*6.06.03.0 mm • x* 58 58 15 cm • X emittance 20 20 33 nm-rad • Estimated sy* 2.2 2.2 2 mm • Bunch spacing 2.4 2.4 0.6 m • Number of bunches 1284 1284 5018 • Collision angle 11crab15 (crab) mrads • Beam pipe radius 2.01.5 1-2 cm • Luminosity 1.0610342-310342-61035cm-2 sec-1

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