The long range beam-beam interaction at CESR-experiments, simulation and phenomenology

A direct route to higher luminosity at colliding beam storage rings is to increase the average beam current by increasing the number of bunches in each beam. However, as the number of bunches increases, so does the number of crossing points where bunches from opposing beams may interact destructively. The most obvious result of these long range interactions, (often seen at CESR), is poor beam lifetime. An increasingly important issue is then how to determine the minimum separation required for adequate lifetime. We have conducted fairly extensive experiments at CESR to measure the minimum separation using a variety of different optics, crossing points, beam currents, and energies