Accelerator physics issues for future electron-ion colliders

The parameters of some of the rings to store heavy ions, in order to collide them with electrons were discussed. The ring-ring and linac-ring scenarios using electron relativistic heavy ion colliders (RHIC) were compared. In the ring-ring scenario, pre-polarized electrons are injected into an electron storage ring from a full energy booster. In the linac-ring scenario the beam circulates only before the recovery of the average electron beam power. The energy recovery linac (ERL) is superconducting in a linac-ring design, constructed of superconducting niobium cavities.