BNL, Upton, Long Island, New York, USA
Barth Electronics, Boulder City, USA
The installation of the Electron Lenses in RHIC will be completed this year. Its design includes a series of drift tubes through which the electron beam copropagates, with the RHIC proton beams. These drift tubes are used to create an electric field gradient to sweep out ions that become trapped within the central magnetic field where the electron beam interacts with the proton beams. These isolated drift tubes are biased by high voltage power supplies. Without a path for the proton beam image currents, high voltages will develop on the drift tubes that can be detrimental to the electron beam and increase the RHIC machine impedance. This paper presents the design of the drift tubes, axial electric field gradient, and the custom high voltage RF bias tees that were designed to provide separate paths for the high frequency image currents and the DC high voltage bias over the same cables. The design and simulation of the bias tee is discussed, as well as RF signals from the proton beam current imaged on the drift tubes, as measured through the bias tees during the commissioning of the blue RHIC beam electron lens this past spring.
BNL, Upton, Long Island, New York, USA
There is a strong interest in running RHIC at low ion beam energies of 2.5-20GeV/nucleon; this is much lower than the typical operations with 100GeV/nucleon. The primary motivation for this effort is to explore the existence and location of the critical point on the QCD phase diagram. Electron cooling can increase the average integrated luminosity and increase the length of the stored lifetime. Simulations and conceptual cooling sub-system designs are underway. The present plan is to provide 10–50mA of bunched electron beam with adequate quality and an energy range of 0.9–5MeV. The preliminary cooling facility configuration planned to be fully inside the RHIC tunnel will include a 102.74MHz SRF gun, a booster cavity, a beam transport to the Blue ring to allow electron-ion co-propagation for ~10-20m, then a 180 degree u-turn electron transport so the same electron beam can similarly cool the Yellow ion beam, then to a dump. The electron beam instrumentation systems that will be described include current transformers, BPMs, profile monitors, a pepper pot emittance station and loss monitors.