1. 2nd Workshop on a Super B-Factory INFN-LNF, Frascati, Italy
IR Design
M. Sullivan
for the
2nd Workshop on a Super B-Factory
March 16-18, 2006
INFN-LNF, Frascati, Italy

2. Outline Starting point Design considerations First attempt at a design
ILC style design
Beam parameters
Design considerations
Andrei’s MAD deck
Pantaleo’s novel idea
Beam pipe and magnet apertures
SR fans
First attempt at a design
Still to do…
Summary

3. ILC type collision Very small spot sizes Large crossing angle
Small emittances
Large beta functions

4. Parameters from Pantaleo’s presentation
Optimized flat case in multi-turn regime with Np=2^10^10,
Nbunches=5000 (3Km ring), Colliding every turn
IP parameters:
sigx=2.67um sigy=12.6nm Crab focus on in vertical plane
betx=2.5mm bety=80um
X_crossing_angle=2*25mrad
sigz=4mm sige=5MeV (sige/e=1*10-3) (Lum_sige=7MeV)
emix=0.4nm (emix_norm=4um)
emiy=0.002nm (emiy_norm=20pm)
emiz=4.0um
Damping_time (Tau)=10msec
Stored time between collision=10usec=0.001Tau=1turn
Collision_frequency=100KHz*5000
Lmultiturn=0.8*10^36 (Lsingleturn=1.2*10^36)
Vertical tune shift like in PEP!!! (similar currents,100 times
more luminosity, 100 times smaller betay)

5. Some IP Parameters Beta x (mm) 2.5 2.5 Beta y (mm) 0.08 0.08
HER LER
Beta x (mm)
Beta y (mm)
Emittance x (nm-rad)
Emittance y (nm-rad)
Sigma x (m)
Sigma y (m)
Bunch spacing (m) 0.6
Crossing angle (mrad) ±25
Luminosity 1036

6. Design Considerations
Used a MAD deck from Andrei to get started
Magnet strengths
Magnet positions
The quad closest to the IP is shared
Panta’s idea is to use a shared sextupole as well
The beams are off axis in the sextupole
More on this…
The shared quad and sextupole have to have a large enough apertures to accommodate both beams
The SR fans have to be followed

7. Shared sextupole
The shared quadrupole has to be optimized for the incoming beam
This means the outgoing beam (which has a different energy) is getting either too little or too much focusing
Enter the shared sextupole
With a shared sextupole and with the beams separated the sextupole introduces a quadrupole term to each beam that is opposite in sign
This allows us to add quad strength to the HER and at the same time subtract quad strength from the LER
And vice versa on the other side of the IP
Several possibilities exist
Incoming beams on axis with the sextupole, outgoing beams off axis
Sextupole axis between the two beam trajectories
Caveat: The beam focusing is dependent on the beam orbit

8. First attempt at a design
Crossing angle of 50 mrad total (±25 mrad)
Beam energies of 4 and 7 GeV
Separate beam pipes at 2.25 m – in front of the second quad
The beta functions are presently not well matched to any sort of transport lines
Put the shared quad and shared sextupole on the same axis – between the two beams (0 deg in the picture)
The shared quad (QD0) together with the crossing angle separate the 2 beams

10. Layout of IR orbits for ILC version Super B Factory

13. More to do More back and forth with the optics people
Trace out the SR fans – make sure they do not fry the IP beam pipe
Trace out the SR from the focusing elements – for detector bkgd masking
Radiative Bhabhas. Where do they go?
Beam-gas bkgds
Find minimum radius beam pipe for IP – probably needs water cooling
HOM power

14. Summary Coming from the ILC design is an interesting approach
Shared sextupole allows for a better optics match between the different beam energies
Large crossing angle helps to separate the beams
Very preliminary first look shows promise…