Projections of Potential Luminosity Improvement for Low-Energy RHIC Operation with Electron Cooling
Electron cooling was proposed to increase luminosity of the RHIC collider for heavy ion beams at low energies. Luminosity decreases as the square of bunch intensity due to the beam loss from the RF bucket as a result of the longitudinal intra beam scattering (IBS), as well as due to the transverse emittance growth because of the transverse IBS. Both transverse and longitudinal IBS can be counteracted with electron cooling. If IBS were the only limitation, this would allow one to keep the initial peak luminosity close to constant throughout the store essentially without the beam loss (provided that loss of ions due to recombination is counteracted, and acceptance of the RF bucket is sufficient). In addition, the phase-space density of the hadron beams can be further increased by providing stronger electron cooling. Unfortunately, the defining limitation for low energies in RHIC is expected to be the space charge, which prohibits strong cooling at lowest energies of interest.