Progress on eRHIC Design

The nuclear physics community endorses strongly the construction of an Electron Ion Collider (EIC). The US nuclear physics community published a White Paper [1] which requires an EIC with a luminosity of 10³³cm^-2s^-1 - 10³⁴cm^-2s^-1, a center of mass energy range of 29-140 GeV, high longitudinal spin polarization of ~70% in both hadron and electron beams, and a large detector acceptance. BNL is proposing eRHIC which makes use on the existing RHIC ion-ion collider complex with the addition of an 5-18 GeV electron storage ring and an 18 GeV rapid cycling injector synchrotron. A SLAC-type polarized electron source provides the polarized electron bunches for the electron storage ring. The design parameters ask for 1-2.5 amps of electron beam current and 1 amp of hadron beam current. Both beams are flat in collisions (horizontal size larger than the vertical one) and the beam-beam parameters correspond to values as have been demonstrated in Hadron-Hadron collision (hadron beam-beam tune shift Dn =0.012) and lepton-lepton collisions (Dn =0.1) respectively. The electron storage ring needs superconducting cavities with variable coupling high power input couplers. The most challenging feature of eRHIC is strong hadron cooling which is based on micro-bunched coherent electron cooling, a novel electron cooling technique. This is required to reach the highest luminosity of 10³⁴cm^-2s^-1. Without cooling the luminosity still reaches 4.4 x 10³³cm^-2s^-1, well within the range given by the White Paper. The design team has completed the preconceptual design, the conceptual design process is underway. The present paper gives an overview and reports on the status of eRHIC development

[1] A. Accardi et al., “Electron Ion Collider: The Next QCD Frontier,” Eur. Phys. J., vol. A52, no. 9, p. 268, 2016