Electron Beam Dynamics in the CERN PS

The 28 GeV proton synchrotron (PS) forms part of the chain of LEP injectors with the rÿle to accelerate positrons and electrons from 0.6 GeV, the operating energy of the Electron/Positron Accumulator (EPA), to 3.5 GeV, the positron/electron injection energy of CERN´s 400 GeV proton synchrotron (SPS) which then accelerates the particles to 20 GeV. The PS used as an electron synchrotron has to supply the SPS with 8 bunches at an intensity of Nb = 8 × 109 particles per bunch. Bunch length and energy spread must be chosen carefully to avoid transverse and longitudinal single-bunch instabilities (turbulence) associated with high peak currents in the SPS. Analysis of the beam dynamics in the combined function lattice of the PS shows that this requirement can be fulfilled if the damning-partition numbers are changed. A Robinson Wiggler is proposed for this purpose and a new additional RF system is needed to produce the required bunch dimensions in longitudinal phase space.