Upgrading RHIC for higher luminosity

Abstract

While RHIC has only just started running for its heavy ion physics program, in the first run last summer, we achieved 10% of the design luminosity. In this paper we discuss plans for increasing the luminosity by a factor of 35 beyond the nominal design. A factor of 4 should be straightforward by doubling the number of bunches per ring and squeezing the β* from 2 to 1 m at selected interaction points. An additional factor of 8 to 10 could be possible by using electron cooling to counteract intrabeam scattering and reduce emittances of the beams.

Optic issues in ongoing ERL projects

“…[23,25]. Table 3 gives a brief summary of the electron beam parameters for the collider and light source mode of eRHIC operation.…”

“…GaAs photocathode driven by a high power circularly polarized laser beam from a small size free-electron laser (also driven by a smaller ERL) [25].…”

“…Using the ERL with a low emittance electron beam dramatically simplifies the lattice of the interaction region [25,35]. Single pass interaction of electrons with the ions and very low emittance of the electron beam allows the use of large β* (~1 meter) for the electron beam, while matching the transverse size of electron and hadron beams.…”

“…These programs are aimed towards a ten-fold luminosity increase at the Relativistic Heavy Ion Collider (RHIC) [24] and development of an ERL-based electron-ion collider, known as eRHIC [25,26]. As part of this program, we are designing, constructing and commissioning a dedicated ERL for R&D studies of issues relevant to operating with high current, high brightness electron beams [27].…”