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IR Design. M. Sullivan for the 2 nd Workshop on a Super B-Factory March 16-18, 2006 INFN-LNF, Frascati, Italy. Outline. Starting point ILC style design Beam parameters Design considerations Andrei’s MAD deck Pantaleo’s novel idea Beam pipe and magnet apertures SR fans
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IR Design M. Sullivan for the 2nd Workshop on a Super B-Factory March 16-18, 2006 INFN-LNF, Frascati, Italy
Outline • Starting point • 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
ILC type collision • Very small spot sizes • Large crossing angle • Small emittances • Large beta functions
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)
Some IP Parameters HER LER • Beta x (mm) 2.5 2.5 • Beta y (mm) 0.08 0.08 • Emittance x (nm-rad) 0.4 0.4 • Emittance y (nm-rad) 0.002 0.002 • Sigma x (m) 2.67 2.67 • Sigma y (m) 0.0126 0.0126 • Bunch spacing (m) 0.6 • Crossing angle (mrad) ±25 • Luminosity 0.81036
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
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
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
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
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…