BNL, Upton, Long Island, New York
Intra-beam scattering (IBS) is the limiting factor of the luminosity lifetime for RHIC operation with heavy ions. Over the last few years the process of IBS was carefully studied in RHIC with dedicated IBS measurements and their comparison with the theoretical models. Recently, in order to suppress transverse IBS growth, a new lattice was designed and implemented in RHIC, which lowered the average arc dispersion by 30%. This lattice became operational during RHIC Run-8. We review the IBS suppression mechanism, IBS measurements before and after the lattice change, and comparisons with predictions.
BNL, Upton, Long Island, New York
MIT, Middleton, Massachusetts
The design status of the high luminosity electron-ion collider, eRHIC, is presented. The goal of eRHIC will be to provide collisions of electrons and possibly positrons) on ions and protons in the center-of-mass energy range from 25 to 140 GeV, at luminosities exceeding 1033 cm-2s-1. A considerable part of the physics program calls for a high polarization level of electrons, protons and He3 ions. The electron beam is accelerated in a recirculating energy recovery linac. Major R&D items for the electron beam include the development of a high intensity polarized source, studies of various aspects of energy recovery technology for high power beams and the development of compact magnets for recirculating passes. In a linac-ring scheme the beam-beam interaction has several very specific features which have to be thoroughly studied. In order to maximize the collider luminosity, several upgrades of the existing RHIC accelerator are required. Those upgrades may include the increase of total beam intensity as well as transverse and longitudinal cooling of ions and protons.