Accelerator physics issues in eRHIC

The accelerator physics issues associated with adding electron–gold and polarized electron–proton collisions to the RHIC repertoire are discussed. Two scenarios are considered: ring–ring and linac–ring collisions. In the first scenario a third electron ring, possibly made from permanent magnets, is added to the RHIC tunnel. In the second scenario the considerable beam power is recuperated by recycling the beam through the full energy linac injector. Straw man ring optics are presented, including an integrated spin rotator which provides longitudinally polarized electrons at the interaction points. Electron and ion intensity limitations are investigated, for operations with as many as 2520 bunches. Synchrotron radiation, beam–beam, electron cloud, and cryogenic heat load limits are examined. The implications for new and upgraded ion ring systems are discussed, including electron cooling, RF systems, the ion abort dumps, and injection and extraction kickers.