Author: Minty, M.G.
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MOPF04 RHIC Injection Transport Beam Emittance Measurements 45
 
  • J.Y. Huang
    Duke University, Durham, North Carolina, USA
  • D.M. Gassner, M.G. Minty, S. Tepikian, P. Thieberger, N. Tsoupas, C.M. Zimmer
    BNL, Upton, Long Island, New York, USA
 
  The Alternating Gradient Synchrotron (AGS)-to-Relativistic Heavy Ion Collider (RHIC) transfer line, abbreviated AtR, is an integral component for the transfer of proton and heavy ion bunches from the AGS to RHIC. In this study, using 23.8 GeV proton beams, we focused on factors that may affect the accuracy of emittance measurements that provide information on the quality of the beam injected into RHIC. The method of emittance measurement uses fluorescent screens in the AtR. The factors that may affect the measurement are: background noise, calibration, resolution, and dispersive corrections. Ideal video Offset (black level, brightness) and Gain (contrast) settings were determined for consistent initial conditions in the Flag Profile Monitor (FPM) application. Using this information, we also updated spatial calibrations for the FPM using corresponding fiducial markings and sketches. Resolution error was determined using the Modulation Transfer Function amplitude. To measure the contribution of the beam’s dispersion, we conducted a scan of beam position and size at relevant Beam Position Monitors (BPMs) and Video Profile Monitors (VPMs, or “flags”) by varying the extraction energy with a scan of the RF frequency in the AGS. The combined effects of these factors resulted in slight variations in emittance values, with further analysis suggesting potential discrepancies in the current model of the beam line’s focusing properties. In the process of testing various contributing factors, a system of checks has been established for future studies, providing an efficient, standardized, and reproducible procedure that might encourage greater reliance on the transfer line’s emittance and beam parameter measurements.  
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MOPF05 Instrumentation for the Proposed Low Energy RHIC Electron Cooling Project with Energy Recovery 49
 
  • D.M. Gassner, A.V. Fedotov, R.L. Hulsart, D. Kayran, V. Litvinenko, R.J. Michnoff, T.A. Miller, M.G. Minty, I. Pinayev, M. Wilinski
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
There is a strong interest in running RHIC at low ion beam energies of 7.7-20 GeV/nucleon [1]; this is much lower than the typical operations with 100 GeV/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. A cooling system is being designed that will provide a 30 – 50 mA electron beam with adequate quality and an energy range of 1.6 – 5 MeV. The cooling facility is planned to be inside the RHIC tunnel. The injector will include a 704 MHz SRF gun, a 704 MHz 5-cell SRF cavity followed by a normal conducting 2.1 GHz cavity. Electrons from the injector will be transported to the Yellow RHIC ring to allow electron-ion co-propagation for ~20 m, then a 180 degree U-turn electron transport so the same electron beam can similarly cool the Blue ion beam. After the cooling process with electron beam energies of 1.6 to 2 MeV, the electrons will be transported directly to a dump. When cooling with higher energy electrons between 2 and 5 MeV, after the cooling process, they will be routed through the acceleration cavity again to allow energy recovery and less power deposited in the dump. Special consideration is given to ensure overlap of electron and ion beams in the cooling section and achieving the requirements needed for cooling. The instrumentation systems described will include current transformers, beam position monitors, profile monitors, an emittance slit station, recombination and beam loss monitors.
 
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MOPF09 Absolute Beam Emittance Measurements at RHIC Using Ionization Profile Monitors 64
 
  • M.G. Minty, R. Connolly, C. Liu, T. Summers, S. Tepikian
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
In this report we present studies of and measurements from the RHIC ionization profile monitors (IPMs). Improved accuracy in the emittance measurements has been achieved by (1) continual design enhancements over the years, (2) application of channel-by-channel offset corrections and gain calibrations in the beam profile measurements and (3) use of measured beta functions at the locations of the IPMs. The removal of systematic errors in the emittance measurements was confirmed by the convergence of all four planes of measurement (horizontal and vertical planes of both the Blue and Yellow beams) to a common value during beam operations with stochastic cooling. Consistency with independent measurements (luminosity-based using zero degree counters) at the colliding beam experiments STAR and PHENIX was demonstrated.
 
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MOPD02 The Electron Backscattering Detector (eBSD), a New Tool for the Precise Mutual Alignment of the Electron and Ion Beams in Electron Lenses 129
 
  • P. Thieberger, Z. Altinbas, C. Carlson, C. Chasman, M.R. Costanzo, C. Degen, K.A. Drees, W. Fischer, D.M. Gassner, X. Gu, K. Hamdi, J. Hock, Y. Luo, A. Marusic, T.A. Miller, M.G. Minty, C. Montag, A.I. Pikin, S.M. White
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
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.
 
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TUPF02 Proposed Pulse Stretching of BPM Signals for the Position Determination of Very Short and Closely Spaced Bunches 294
 
  • P. Thieberger, S.J. Brooks, K. Hamdi, R.L. Hulsart, G.J. Mahler, R.J. Michnoff, M.G. Minty, D. Trbojevic
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
A proposal for a future ultra relativistic polarized electron-proton collider (eRHIC) is based in part on the transport of multiple electron beams of different energies through two FFAG beam transports around the 3834 m long RHIC tunnel circumference in order to recirculate them through an Energy Recovery Linac for their stepwise acceleration and deceleration. For each of these transports, the beams will travel in a common vacuum chamber, horizontally separated from each other by a few mm. Determining the position of the individual bunches is challenging due to their very short length (~12 ps rms) and their temporal proximity (less than 4 ns in some cases). Providing pulses adequate for accurate sampling is further complicated by the less-than-ideal response of long coaxial cables. Here we propose two approaches to produce enhanced, i.e. stretched pulse shapes of limited duration; one based on specially shaped BPM electrodes and the other one on analog integration of more conventional stripline BPM signals. In both cases, signals can be generated which contain relatively flat portions which should be easier to sample with good precision without requiring picoseconds timing accuracy.
 
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