Performance of the PEP-II B-Factory Collider at SLAC
PEP-II is an e+e-asymmetric B-Factory Collider located at SLAC operating at the Upsilon 4S resonance (3.1 GeV x 9 GeV). It has reached a luminosity of 9.21×1033/cm2/s and has delivered an integrated luminosity of 710 pb-1in one day. PEP-II has delivered, over the past six years, an integrated luminosity to the BaBar detector of over 262 fb-1. PEP-II operates in continuous injection mode for both beams boosting the integrated luminosity. The peak positron current has reached 2.45 A in 1588 bunches. Steady progress is being made in reaching higher luminosity. The goal over the next several years is to reach a luminosity of 2.1x1034/cm2/s. The accelerator physics issues being addressed in PEP-II to reach this goal include the electron cloud instability, beam-beam effects, parasitic beam-beam effects, high RF beam loading, shorter bunches, loweryinteraction region operation, and coupling control. Figure 1 shows the PEP-II tunnel.
PEP-II and KEKB Operational Status
The present two B-Factories, PEP-II at SLAC in California and KEKB at KEK in Tsukuba, Japan, operate at the Upsilon 4S and have reached parameter levels unprecedented for e+e- colliders. They have provided very large data samples for their respective particle detectors, BaBar and BELLE. Luminosity has exceeded 1.5 x 1034/cm2/s. Beam currents have reached 2.5 A with 1600 positron bunches spaced by 4 nsec. Continuous injection with the detectors taking data has added significantly to data collection rates by about 40%. Bunch-by-bunch feedback systems damp strong longitudinal and transverse coupled bunch instabilities. The beam-beam interaction has allowed high tune shift levels even in the presence of parasitic crossing and crossing angle effects. Both B-Factory colliders have significant near term luminosity improvement programs.
Simulation of the beam halo from the beam-beam interaction.
The luminosity lifetimes of e{sup +}e{sup {minus}} colliders are often dominated by the halo produced by the beam-beam interaction. They have developed a simulation technique to model this halo using the flux across boundaries in amplitude space to decrease the CPU time by a factor of one-hundred or more over `brute force` tracking. It allows simulation of density distributions and halos corresponding to realistic lifetimes. Reference 1 shows the agreement with brute force tracking in a number of cases and the importance of beam-beam resonances in determining the density distribution of large amplitudes. this research is now directed towards comparisons with operating colliders and studies of the combined effects of lattice and beam-beam nonlinearities. LEP offers an ideal opportunity for both, and in this paper they are presenting the first results of LEP simulations.