PEP stores electrons and positrons

PEP celebrated its first stored electron beam on 21 April. On 5 May both positron and electron beams were stored, each at 8 GeV; since then beam currents of 2 mA for electrons and 1.5 mA for positrons have been reached. PEP director John Rees explained that the currents were deliberately kept low to avoid the incoherent beam‐beam limit. As commissioning continues, the PEP team will bring the beams to 15 GeV each, where peak performance is expected. The maximum design energy is 18 GeV/beam.