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PEP II RF System

Stage II of PEP consists of adding a superconducting proton storage ring to the electron-positron ring now completing construction. To obtain the desired luminosity between the tightly bunched electron beam and the protons, the protons will be tightly bunched also. The proton bunch length and the number of bunches imposes unusual requirements on the RF system. Acclerating to full proton energy makes the bunching easier. PEP is a positron, electron colliding beam storage ring being constructed as a joint project between the Stanford Linear Accelerator Center and the Lawrence Berkeley Laboratory at the SLAC site. It has a design value of 15 GeV on 15 GeV with a luminosity of 1032 and energy up to 18 GeV with reduced luminosity due to reduced current. The target date for beam turn-on is October 1, 1979. The original concept included protons, electrons and positrons, hence PEP. However, the proton ring required superconducting magnets to fit a 200 GeV ring on the SLAC site. A decision was taken in 1974 to proceed with the electron, positron portion, since conventional techniques were available for the construction; and to wait for development of the magnets before proposing the addition of the proton ring. It appears possible to develop magnets with fields of 8 tesla so that a proton energy of 350 GeV could be contained in the PEP tunnel.