Recent and Past Experiences with Beam-Beam Effects at HERA

Proton beam stability when in collision with high current electron bunches was of foremost concern during the design stages of the HERA collider[1]. In initial commissioning the beam-beam interaction proved to be a key factor in determining the lifetime of the proton beam. It was quickly ascertained[2] that the proton beam lifetime in collision could be substantially increased by both matching the electron and proton beam sizes ( ) at the interaction points (IPs) and by carefully centering the beams. Presently, proton beam life times of hundreds of hours are routinely observed. In the near future, the accelerators will be upgraded[3] to include new low- insertions and to allow for yet higher beam currents. Key factors affecting the stability of colliding proton beams will be described as well as recent experiments performed to explore at high electron beam currents new regimes of the proton beam-beam limit at HERA.