IR Up Grade Plans for the PEP-II B-Factory

PEP-II, the SLAC, LBNL, LLNL B-factory has achieved a peak luminosity of over 9×10 33 cm -2 s -1 , more than 3 times the design luminosity, and plans to obtain a luminosity of over 1×10 34 cm -2 sec -1 in the next year. In order to push the luminosity performance of PEP-II to even higher levels an upgrade to the interaction region (IR) is being designed. In the present design, the interaction point (IP) is a head-on collision with two strong horizontal dipole magnets located between 21-70 cm from the IP that bring the beams together and separate the beams after the collision. The first parasitic crossing (PC) is 63 cm from the IP in the present by2 bunch spacing. Future improvements to PEP-II performance include lowering the βy * values of both rings. This will increase the βy value at the PCs which increases the beambeam effect at these non-colliding crossings. Introducing a horizontal crossing angle at the IP quickly increases the beam separation at the PCs but recent beam-beam studies indicate that a significant luminosity reduction occurs when a crossing angle is introduced at the IP. We discuss these issues and describe the present interaction region upgrade design.