Electron Storage Ring Design for the Future Electron-Ion Collider at Brookhaven National Laboratory

The Electron-Ion Collider (EIC), which is currently being designed for construction at Brookhaven National Laboratory, will collide polarized electron beams (5-18 GeV) with polarized hadron beams (41-275 GeV) at luminosities up to 10³⁴ cm⁻² s⁻¹. The EIC will be the only lepton-hadron collider after HERA and, in contrast to that earlier machine, will feature high polarization in both beams, a wide range of center-of-mass collision energies, and much higher luminosities. Designing a collider that is capable of achieving these goals, within the physical constraints imposed by an existing tunnel as well as cost constraints, represents a significant challenge, which calls for original solutions. Two electron rings—a synchrotron and a storage ring—are being designed to be built in the existing tunnel. Recently, significant progress has been made on advancing the storage ring design, which is complicated by the need to provide a wide range of energies while matching the beam size and revolution times to the hadron beam, the need to rotate the spin vector at the interaction point and maintain high polarization, and the challenging dynamic-aperture requirements.