Positron-Electron Multicycle Injection at the CEA Colliding Beam Project

We have developed a reliable procedure for multicycle filling of the Cambridge Electron Accelerator ring with positrons and electrons. The positron fill rate is determined by the intensity, spectrum, and emittance provided by the 125-MeV positron linac and also by the available phas-space and momentum acceptance aperture of the synchrotron for off-axis injection. This aperture in turn depends on the width of the already stored beam. Losses of newly injected particles in subsequent acceleration cycles depend on the extent of radiation damping provided by special damping magnets. After measuring and optimizing the main parameters, we have achieved a positron fill rate of 0. 4 mA peak per second. The control system used in rapid change over from 125-MeV positron injection to 250-MeV electron injection is sufficiently stable, automatic, and fast acting that filling the ring with countertraveling positron and electron beams takes less than five minutes.