BNL, Upton, Long Island, New York
The fundamental questions about QCD which can be directly answered at Relativistic Heavy Ion Collider (RHIC) call for large integrated luminosities. The major goal of RHIC-II upgrade is to achieve 10 fold increase in luminosity of Au ions at the top energy of 100 GeV/n. A significant increase in luminosity for polarized protons is also expected, as well as for other ion species and for various collision energies. Such a boost in luminosity for RHIC-II is achievable with implementation of high-energy electron cooling. The design of the higher-energy cooler for RHIC recently adopted a non-magnetized approach which requires a low temperature electron beam. Such high-intensity high-brightness electron beams will be produced with superconducting Energy Recovery Linac (ERL). Detailed simulations of the electron cooling process and numerical simulations of the electron beam transport including the cooling section were performed. An intensive R&D of various elements of the design is presently underway. Here, we summarize progress in these electron cooling efforts.
Tech-X, Boulder, Colorado
BNL, Upton, Long Island, New York
Novel electron-hadron collider concepts are a high priority for the long-term plans of the international nuclear physics community. Orders of magnitude higher luminosity will be required for the relativistic ion beams in such particle accelerators. Electron cooling of highly relativistic ions is under consideration for the proposed RHIC II luminosity upgrade. The parallel VORPAL code is being used for molecular dynamics simulations of the friction force on individual ions, given expected parameters of the RHIC II cooling system, including the effects of an idealized helical undulator magnet and of estimated magnetic field errors. The well-known analytical formula for the field-free case is the basis for physical intuition regarding dynamical friction, but this is derived under the assumption of very long interaction times and symmetric ion/electron collisions. For RHIC II parameters, the interaction time is short compared to the electron plasma frequency, so there is essentially no shielding of the ion charge and one must consider finite time effects and asymmetric collisions. We present the current status of this work.
JINR, Dubna, Moscow Region
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois
BNL, Upton, Long Island, New York
JINR, Dubna, Moscow Region
A 0.1-0.5 A, 4.3 MeV DC electron beam provides cooling of 8 GeV antiprotons in Fermilab's Recycler storage ring. Properties of electron cooling have been characterized in measurements of the drag force, cooling rates, and equilibrium distributions. The paper will report experimental results and compare them with modeling by BETACOOL code.
BNL, Upton, Long Island, New York
Recently, a strong interest emerged in running RHIC at low energies in the range of 2.5-25 GeV/n total energy of a single beam. Providing collisions in this energy range, which in RHIC case is termed “low-energy” operation, will help to answer one of the key questions in the field of QCD about existence and location of critical point on the QCD phase diagram. Applying electron cooling directly at these low energies in RHIC would result in dramatic luminosity increase, small vertex distribution and long stores. On the other hand, even without direct cooling in RHIC at these energies, significant luminosity gain can be achieved by decreasing the longitudinal emittance of the ion beam before its injection into RHIC from the AGS. This will provide good RF capture efficiency in RHIC. Such an improvement in longitudinal emittance of the ion beam can be provided at by a simple electron cooling system at injection energy of AGS. Simulations of electron cooling both for direct cooling at low-energies in RHIC and for pre-cooling in AGS were performed, and are summarized in this report.