Design studies of high-luminoisty ring-ring electron-ion collider at CEBAF

Experimental studies of fundamental structure of nucleons require an electron-ion collider of a center-of- mass energy up to 90 GeV at luminosity up to 10³⁵ cm^-2 s^-1 with both beams polarized. A CEBAF-based collider of 9 GeV electrons/positrons and 225 GeV ions is envisioned to meet this science need and as a next step for CEBAF after the planned 12 GeV energy upgrade of the fixed target program. A ring-ring scheme of this collider developed recently takes advantage of the existing polarized electron CW beam from the CEBAF and a green-field design of an ion complex with electron cooling. We present a conceptual design and report design studies of this high-luminosity collider.