Machine Summary of SuperB workshop in Hawaii

1. Machine Summary of SuperB workshop in Hawaii • PEP-II now • KEKB now • PEP-II upgrade • Super B PEP (e36) • Super KEKB • Summary • urls used found at: • http://www.phys.hawaii.edu/~superb04/slides.html • Flanagan • Tajima • Tabelsi • Sullivan

2. Machine Parameters that are Important for the IR PEP-II KEKB LER energy 3.1 3.5 GeV HER energy 9.0 8.0 GeV LER current 1.96 1.51 A HER current 1.32 1.13 A y* 12.5 6.5 mm x* 25 60 cm X emittance 50 20 nm-rad Estimated sy* 5 2.2 mm Bunch spacing 1.26 2.4 m Number of bunches 1317 1284 Collision angle head-on 11 mrads Beam pipe radius 2.5 1.5 cm Luminosity 7.21033 11.31033 cm-2 sec-1

3. Present IR (for reference)

4. Radiative Bhabhas

5. Radiative Bhabhas

7. Touschek

8. PEP-II Proposed Upgrade Plans • Now Projected Upgrade • LER energy 3.1 3.1 3.1 GeV • HER energy 9.0 9.0 9.0 GeV • LER current 1.8 3.6 4.5 A • HER current 1.0 1.8 2.0 A • y*12.58.56 mm • x* 28 28 28 cm • X emittance 50 40 40 nm-rad • Estimated sy* 4.9 3.6 2.7 mm • Bunch spacing 1.89 1.26 1.26 m • Number of bunches 1034 1500 1700 • Collision angle head-on head-on head-on mrads • Beam pipe radius 2.5 2.5 2.5 cm • Luminosity 6.61033 1.81034 3.31034cm-2 sec-1

9. Crossing angle and parasitic crossings • Crossing angle • Early last year, Ohmi-san from KEK announced that his beam-beam simulation code indicated a rapid luminosity degradation as a function of increasing crossing angle. Last summer, Yunhai Cai at SLAC confirmed Ohmi’s beam-beam result. The effect is most pronounced for very high tune shifts (~0.1). • Parasitic crossings • The introduction of a crossing angle increases the beam separation at the parasitic crossings which would lower the effect we presently see from parasitic crossings in by2 bunch patterns. Lowering by* also increases parasitic crossing effects since the by at the PC is larger.

10. Plot of luminosity degradation as a function of increasing crossing angle (courtesy of Yunhai Cai)

11. Present Working Design • Stronger B1 magnet to increase separation at 1st parasitic crossing 20% stronger first 5 slices (first 12.5 cm with the weakest field and the largest lever arm) • Slightly increase the beam energy asymmetry 9.1 x 3.08 GeV • Stronger, closer QD1 magnets 30% stronger slices for 1st 5 slices Move radial ion pump behind B1 to behind QD1 Put higher strength focusing in present pump place Minimal hardware change Higher strength material has higher temperature coefficient

12. Modified Head-on design

13. PEP-III Super B • Now Projected Upgrade Super B • LER energy 3.1 3.1 3.1? 3.5 GeV • HER energy 9.0 9.0 9.0? 8.0 GeV • LER current 1.8 3.6 4.5 22.2 A • HER current 1.0 1.8 2.0 9.7 A • y*12.58.56.51.5 mm • x* 28 28 28 15 cm • X emittance 50 40 40 70 nm-rad • Estimated sy* 4.9 3.6 2.7 1.7 mm • Bunch spacing 1.89 ~1.5 1.26 0.63 m • Number of bunches 1034 1500 1700 3400 • Collision angle head-on head-on 03.2512-14 mrads • Beam pipe radius 2.5 2.5 2.5 1.5-2.0? cm • Luminosity 6.61033 1.81034 3.3103411036 cm-2 sec-1

14. 3rd attempt • Asymmetric optics (again a la KEK) • The upsteam QD1 magnet for the LER is essentially on axis • The magnet locations are still symmetric (+/-Z) • Still have some upstream bending but the fans are greatly reduced from the previous symmetric optics case. The main SR fans still clear the local IR. • +/- 14 mrad crossing angle • The larger crossing angle is needed to keep the QF2 magnet at the 2.5m point from the IP • This large a crossing angle opens up the possibility of filling all 6800 bunches if the RF freq. is doubled

16. SuperKEKB Machine Parameters

17. Interaction Region • Move final focus quadrupoles closer to IP for lower beta functions at IP. • Preserve current machine-detector boundary. • Rotate LER 8 mrad. • QCS and solenoid compensation magnets overlap in SuperKEKB. • Issues: • QC1 normal or superconducting? • Dynamic aperture => need damping ring for positrons, at least.

19. Construction Scenario • The upgrade of KEKB to SuperKEKB is proposed for around 2007. • R&D and production of various components will be done in the first four years in parallel with the physics experiment at KEKB. • The installation will be done during a one year shutdown in 2007, and then the commissioning of SuperKEKB will begin.

21. Summary • Belle does not have a luminosity background term because the beams are bent further out from the IR than they are in PEP-II • Belle does have a significant SR background from the HER high power dump located at about 9 m from the IP • The PEP-II luminosity background is most likely radiative bhabhas where the off-energy beam particles are swept out and hit the beam pipe (a feature of head-on collisions) • Touschek events that occur at the IP should be checked as a possible detector background source • The IR upgrade design is presently leaning toward a stronger B1 magnet in order to keep head-on collisions and to increase the parasitic crossing distance

22. Summary cont’d • The PEP-II superB IR design is becoming more similar to the present and future KEKB design in that the upstream radiation fans have become much smaller and have lower power in order to allow for a small radius beam pipe • quadrupole radiation has not been studied yet ---- remember ----1 W of x-rays = 1 Mrad/s • The super KEKB design will have an LOI out in the next couple of months. They now claim they will have a 5e35 luminosity with a factor of 4 increase from the head-on collision effect seen in beam-beam simulations • The schedule for the super KEKB tends to argue that they will not achieve full luminosity until about 2013