Electron-ion collisions at RHIC using a high intensity self-polarizing electron ring

We consider the design of an electron-ion collider realized by adding a self-polarizing electron ring to the existing RHIC collider. It would provide polarized electron-proton and unpolarized electron-ion beam collisions in the center of mass energy range of 30-100 GeV and at luminosities up to 10/sup 33/ cm/sup -2/s/sup -1/ for e-p and 10/sup 31/ cm/sup -2/s/sup -1/ for e-Au collisions. An electron storage ring lattice has been developed which provides a short polarization time for an electron beam in the 5-10 GeV energy range and which satisfies the luminosity goals. We describe the modifications to the RHIC interaction region layout required for both efficient beam separation and also for longitudinal electron and proton beam polarization at the collision point.