M.%20Sullivan

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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

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Outline

• Starting point
• ILC style design
• Beam parameters
• Design considerations
• Andreis MAD deck
• Pantaleos novel idea
• Beam pipe and magnet apertures
• SR fans
• First attempt at a design
• Still to do
• Summary

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ILC type collision

• Very small spot sizes
• Large crossing angle
• Small emittances
• Large beta functions

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Parameters from Pantaleos presentation

• Optimized flat case in multi-turn regime
  with Np21010,
• Nbunches5000 (3Km ring), Colliding every
  turn
• IP parameters
• sigx2.67um sigy12.6nm Crab focus on in
  vertical plane
• betx2.5mm bety80um
• X_crossing_angle225mrad
• sigz4mm sige5MeV (sige/e110-3)
  (Lum_sige7MeV)
• emix0.4nm (emix_norm4um)
• emiy0.002nm (emiy_norm20pm)
• emiz4.0um
• Damping_time (Tau)10msec
• Stored time between collision10usec0.001Ta
  u1turn
• Collision_frequency100KHz5000
• Lmultiturn0.81036 (Lsingleturn1.2103
  6)
• Vertical tune shift like in PEP!!! (similar
  currents,100 times
• more luminosity, 100 times smaller betay)

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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 0.8?1036

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Design Considerations

• Used a MAD deck from Andrei to get started
• Magnet strengths
• Magnet positions
• The quad closest to the IP is shared
• Pantas 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

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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

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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

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Layout of IR orbits for ILC version Super B
Factory
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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

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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