Modeling colliding beams with an element by element representation of the storage ring guide field

A detailed model of the Cornell Electron Storage Ring (CESR) guide field, including beam-beam interaction computed in the weak-strong regime, is the basis for a multiturn simulation of luminosity. The simulation reproduces the dependence of luminosity on bunch current that is measured in the storage ring, at both high-energy (5.3   GeV/beam) and in the wiggler-dominated low energy (CESR-c) configuration (1.9   GeV/beam). Dynamics are determined entirely by the physics of propagation through the individual guide field elements with no free parameters. Energy dependence of the compensation of the transverse coupling introduced by the experimental solenoid is found to significantly degrade specific luminosity. The simulation also indicates a strong dependence of limiting beam-beam tune shift parameter on the geometric mean of synchrotron tune and bunch length.