RHIC Superconducting Accelerator and Electron Cooling Group

RHIC Accelerator R&D Division

Low-Energy Electron Cooling, led by Alexei Fedotov

Recently, a strong interest emerged in running the Relativistic Heavy Ion Collider (RHIC) at low beam total energies of 2.5-20 GeV/nucleon, substantially lower than the nominal beam total energy of 100 GeV/nucleon. Collisions in this low energy range are motivated by one of the key questions of quantum chromodynamics (QCD) about the existence and location of critical point on the QCD phase diagram. Applying electron cooling directly in RHIC will increase the average integrated luminosity significantly, and will provide long stores for physics. For luminosity with cooling we expect that improvement will be limited due to the space-charge effects. We have started APEX experiment at RHIC with main goal to understand whether we can operate with space-charge tune shift DQ>0.05 under collisions, which would provide an additional luminosity improvement with electron cooling, compared to the estimates given above. The electron cooling system needed should be able to deliver an electron beam of adequate quality in a wide range of electron beam energies (0.9-3 MeV). The possibility of a cooler operating at energies up to 5 MeV is also being considered. Our present baseline cooler design is based on existing Fermilab’s Pelletron electrostatic accelerator, which is presently operating at 4.36MeV.