BROOldiAVEN NATIO;NAL LABORATORY MeRHIC -staging approach to eRHIe DISCLAIMER MERRIe -STAGING APPROACH TO ERHIC

Abstract Design of a medium energy electron-ion collider (MeRHIC) is llilder development at the ColliderAccelerator Department at BNL. The design envisions construction of a 4 GeV electron accelerator in a local area inside and near the RHIC tunnel. Electrons will be produced by a polarized electron source and accelerated in energy recovery linacs. Collisions of the electron beam with 100 GeV/u heavy ions or with 250 GeV polarized protons win be arranged in the existing IP2 interaction region of RHIC. The luminosity of electron-proton collisions at the 10 32 cm-2 s-1 level will be achieved with 50 rnA CW electron current and presently available proton beam parameters. Efficient proton beam cooling at collision energy may bring the luminosity to 10 33 cm-2S-1 . An important feature ofMeRHIC is that it serves as a first stage of eRHIC, a future electron-ion collider at BNL with both higher luminosity and energy reach. The majority of MeRHIC accelerator components will be used in eRHIC