1. E. Paloni, S. Bettoni, R. Pantaleo, M Biagini, et al.
IR Design Update
M Sullivan
For
E. Paloni, S. Bettoni, R. Pantaleo, M Biagini, et al.
SuperB Workshop
Elba, Italy
May 31 - Jun 3, 2008

2. Outline CDR design New design Layout SR backgrounds More to do Summary
Overall
With detector
Near the IP
Radiative Bhabhas
SR backgrounds
HER
LER
More to do
Summary

3. CDR Design Shared QD0 Offset outgoing beams
Significant SR power from outgoing offsets
Strong bending also bends the radiative bhabhas

9. New Design QD0 has two centers – one for each beam (septum QD0)
Bore has to be cold – no room for warm bore
Means very low SR power on the walls
Minimal bending of incoming and outgoing beams
QDO centers are parallel to detector axis

10. New Design (2) Final focus magnets are close to the IP
Final soft bend magnets are further outboard
Still include an extra HEB QD0 part
Offset the QD0H quadrupole by -4 mm on the upstream beam line in order to deflect the x-rays from QF1H magnet away from the IP beam pipe and away from the cold bore of the downstream QD0
This offset is presently not on the downstream HER (HER is slightly asymmetric – could be made symmetric or anti-symmetric)

11. New IR design with BaBar

12. New IR design with luminosity gammas

13. New IR design with BaBar

14. New IR design with BaBar
BSC envelopes are 15 sigma + 1 mm

18. Beam parameters used Parameter HER LER Energy (GeV) 7 4
Current (A)
Beta X (mm)
Beta Y (mm)
Emittance X (nm-rad)
Emittance Y (pm-rad)
Sigma X (m)
Sigma Y (nm)

19. Magnet parameters Quad G (k/m) L(m) from IP (m) QD0 -1633 0.25 0.40
QD0H
QF1L
QF1H
Dipole B (kG) L(m) from IP (m)
B1L
B1H

20. Radiative Bhabhas

21. SR Bkgds Masks or beam pipe surfaces HER SR
Dist Radius sigma Power Gammas
(m) (mm) X Watts >10 keV
x109
x107
x107
> x104
> x
x107
x105
On the cold bore
We gain a factor of from SA and a factor of 30 from backscatter rate ~330/crossing -- almost ok?

22. SR bkgds (2) Masks or beam pipe surfaces LER SR
Dist Radius sigma Power Gammas
(m) (mm) X Watts >10 keV
x107
x105
x106
>
>
x103
On the cold bore

23. SR power and bkgds
179 W
45 W
0.2 W
236 W
0.2 W
0.3 W

24. 8288 W
184 W
4 W
1539 W

25. More to do on SR backgrounds
Calculate the rate of photons through the detector beam pipe
Deviate orbit by at least +/- 1 sigma to see if power levels and backgrounds are still ok
Put in compensating solenoids and the detector field
More careful calculation of backscattered photons
Tip scattering rate and incidence on detector beam pipe
Check forward scattered photon rate from upstream soft bend magnets

26. More to do on engineering
Can QD0 be built?
Transition space from warm bore to cold bore
Magic flange location (CESR and KEK have done it)
Bellows location to relieve stress on detector Be beam pipe
Magnet supports
Vacuum supports
Where can we put pumping?
Is QD0H PM or SC? (Probably SC)
Looks like all the final focus magnets are in the detector field (hence all are most likely SC)
Compensating solenoids
Cryostat size
Warm bore for the other IR magnets
30-40 beam sigmas best aperture so far for the present design
One mask is at 23 sigma X

27. HOM calculations
Can’t really do much until we have an engineering design
Need:
The location of joints and bellows
Beam pipe cross-sections
Details about septum junction
Mask locations …
This issue is one of the most difficult ones to get right everywhere. You essentially have to design and then model the entire machine before you can find out if you have any unexpected weaknesses. Even then you usually discover the weakness only after it has bitten you.
The experience of the B-factories (PEP-II and KEKB) has helped to shed light on this issue.

28. Detector beam pipe No doubt Be
Double layer
How thick?
The closer to the beam the more cooling we need
Most likely need Au coating on inside
Thickness TBD
Cooling fluid (gas does not cool enough)

29. Summary
The new IR design looks much better from a lattice point of view
Less bending at the IP
Lower emittance growth
It also looks better from a radiative bhabha background point of view
Minimal bending
With a BaBar cartoon drawn in, it looks like all of the final focus magnets need to be superconducting
More challenges for the cryostat design
A good start but there is much more to do before we have something we know we can build…

30. Extra slides

31. SR power Magnet Dipole (kW) Quad (kW) Total (kW) QD0 4.660
QD0H
QF1L
QF1H
B1L
B1H
Under construction…