BNL, Upton, Long Island, New York, USA
The electron lenses installed in RHIC are equipped with two independent transverse beam profiling systems, namely the Pinhole Detector and YAG screen. A small Faraday cup, with a 0.2mm pinhole mask, intercepts the electron beam while a pre-programmed routine automatically raster scans the beam across the detector face. The collected charge is integrated, digitized and stored in an image type data file that represents the electron beam density. This plungeable detector shares space in the vacuum chamber with a plunging YAG:Ce crystal coated with aluminum. A view port at the downstream extremity of the Collector allows a GigE camera, fitted with a zoom lens, to image the crystal and digitize the profile of a beam pulse. Custom beam profiling software has been written to import both beam image files (pinhole and YAG) and fully characterize the transverse beam profile. The results of these profile measurements are presented here along with a description of the system and operational features.
* W. Fischer, et al, "… head-on beam-beam compensation in RHIC", ICFA (BB3013), CERN (2013).
**T. Miller, et al, “… eLens pin-hole detector and YAG…“, BIW2012, Newport News, VA, TUPG039
BNL, Upton, Long Island, New York, USA
The Relativistic Heavy Ion Collider (RHIC) electron lenses, being commissioned to attain higher polarized proton-proton luminosities by partially compensating the beam-beam effect, require good alignment of the electron and proton beams. These beams propagating in opposite directions in a 5T solenoid have a typical rms width of 300 microns and need to overlap each other over an interaction length of about 2 m with deviations of less than ~50 microns. A new beam diagnostic tool to achieve and maintain this alignment is based on detecting electrons that are backscattered in close encounters with protons. Maximizing the intensity of these electrons ensures optimum beam overlap. The successful commissioning of these devices using 100 GeV/amu gold beams is described. Future developments are discussed that will further improve the sensitivity to small angular deviations.