Interaction region design at the PEP-II B Factory

We describe the Interaction Region (IR) for the PEP-II project, a collaboration of SLAC, LBNL, and LLNL. The near IR region inboard of 3 m from the interaction point (IP) is designed to focus the 3.1 GeV low energy beam (LEB) and bring it into head-on collision with the 9 GeV high energy beam (HEB). We describe the overall design parameters of this area and the integration with the detector geometry. Permanent magnet (PM) dipoles and quadrupoles inside the 1.5 T solenoidal field of the detector are described. The beam separation is initiated by a dipole field made from PM blocks in a stepped conical geometry in order to maximize detector solid angle coverage. The beam separation is completed by a hybrid PM quadrupole - dipole. The vacuum chamber is designed to mask synchrotron radiation (SR) away from the beam pipe located around the IP and to absorb the power (70 kW) generated by the SR, image current losses and higher-order-mode (HOM) losses