Electron cooling of high energy ion beams in RHIC and other facilities

A two-stage Pelletron intermediate energy electron cooling system could cool the 100 GeV/nucleon 197Au79+ beams to be stored in RHIC, the Relativistic Heavy Ion Collider under construction at the Brookhaven National Laboratory, in less than 300 s — 100 times faster than the state of the art stochastic cooling systems that are being proposed. After the beam transverse emittance and longitudinal momentum spread are reduced by initial cooling, the electron cooling time would be further reduced by up to a factor of 3, whereas the stochastic cooling time would increase. The electron cooling time varies in proportion to γ2 whereas the stochastic cooling time is approximately independent of the beam energy; thus the electron cooling system performance is even more impressive at lower energies. The parameters for such a system are presented along with the status of the technology necessary to build such a system. The application of this technology to other existing or proposed lower-energy machines is also briefly reviewed.