Electron pinch effect in beam-beam interaction of ERL based eRHIC

Beam-beam effects present one of major factors limiting the luminosity of colliders. In the linac-ring option of the eRHIC design, an electron beam accelerated in a superconducting energy recovery linac(ERL) collides with a proton beam circulating in the Rille ring. Some specific features of beam-beam interactions should be carefully evaluated for the linac-ring configuration. One of the most important effects on the ion beam stability originates from a strongly focus ed electron beam because of the beam-beam force. This electron pinch effect makes the beam-beam parameter of the ion beam several times larger than the design value, and leads to a fast emittance grow th of the ion beam. The electron pinch effect can be controlled by adjustments of the electron lattice and the incident emittance. We present results of simulations optimizing the ion beam parameters in the presence of this pinch effect