Concepts for High Luminosity Electron-Ion Colliders: Developments and Current Status

Three concepts for a polarized, high luminosity (10$^{33}$-10$^{35}$ cm$^{-2}$ sec$^{-1})$ electron-ion collider (EIC) of 50 -- 150 GeV center-of-mass energy are currently studied in the US: A conventional ring-ring version and a more ambitious linac-ring version of eRHIC collide electrons from a storage ring or in an energy recovery linac with the hadron beams of RHIC. A more futuristic concept involves colliding figure -- 8 shaped electron and hadron storage rings using electrons from CEBAF involving very high bunch collision rings to achieve maximal luminosity. First ideas for an electron-ion collider at the LHC (LHeC) are presented.