Paper |
Title |
Other Keywords |
Page |
MOPCH099 |
Performance and Capabilities of the NASA Space Radiation Laboratory at BNL
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ion, booster, extraction, BNL |
270 |
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- K.A. Brown, L. Ahrens, I.-H. Chiang, C.J. Gardner, D.M. Gassner, L. Hammons, M. Harvey, J. Morris, A. Rusek, P. Sampson, M. Sivertz, N. Tsoupas, K. Zeno
BNL, Upton, Long Island, New York
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The NASA Space Radiation Laboratory (NSRL) at BNL has been in operation since 2003. The first commissioning of the facility took place beginning in October 2002 and the facility became operational in July 2003. The facility was constructed in collaboration with NASA for the purpose of performing radiation effect studies for the NASA space program. The NSRL is capable of making use of protons and heavy ions in the range of 0.05 to 3 GeV/n slow extracted from BNL's AGS Booster. It is also capable of making use of protons and heavy ions fast extracted from the AGS Booster. Many different beam conditions have been produced for experiments at NSRL, including very low intensity In this report we will describe the facility and its' performance over the eight experimental run periods that have taken place since it became operational. We will also describe the current and future capabilities of the NSRL.
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MOPCH101 |
On the Feasibility of a Spin Decoherence Measurement
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polarization, synchrotron, proton, AGS |
276 |
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- W.W. MacKay
BNL, Upton, Long Island, New York
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In this paper, we study the feasibility of making a turn-by-turn spin measurement to extract the spin tune of a synchrotron from a polarized beam injected perpendicular to the stable spin direction. For the ideal case of a zero-emittance beam with no spin-tune spread, there would be no spin decoherence and a measurement of the spin tune could easily be made by collecting turn-indexed polarization data of several million turns. However, in a real beam there is a momentum spread which provides a tune spread. With a coasting beam the tune spread will cause decoherence of the spins resulting in a fast depolarization of the beam in a thousand turns. With synchrotron oscillations the decoherence time can be greatly increased, so that a measurement becomes feasible with summation of the turn-by-turn data from a reasonable number of bunches (100 or fewer). Both the cases of a single Siberian snake and a pair of Siberian snakes are considered.
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MOPCH102 |
A Straight Section Design in RHIC to Allow Heavy Ion Electron Cooling
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electron, interaction-region, dipole, quadrupole |
279 |
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MOPCH132 |
Coupled Maps for Electron and Ion Clouds
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electron, ion, simulation, proton |
354 |
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- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- S. Peggs
BNL, Upton, Long Island, New York
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Contemporary electron cloud models and simulations reproduce second order phase transitions, in which electron clouds grow smoothly beyond a threshold from "off" to "on". In contrast, some locations in the Relativistic Heavy Ion Collider (RHIC) exhibit first order phase transition behaviour, in which electron cloud related outgassing rates turn "on" or "off" precipitously. This paper presents a global framework with a high level of abstraction in which additional physics can be introduced in order to reproduce first (and second) order phase transitions. It does so by introducing maps that model the bunch-to-bunch evolution of coupled electron and ion clouds. This results in simulations that run several orders of magnitude faster, reproduce first order phase transitions, and show hysteresis effects. Coupled maps also suggest that additional dynamical phases (like period doubling, or chaos) could be observed.
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MOPCH133 |
An Analytic Calculation of the Electron Cloud Linear Map Coefficient
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electron, simulation, LHC, heavy-ion |
357 |
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- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- S. Peggs
BNL, Upton, Long Island, New York
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The evolution of the electron density during multibunch electron cloud formation can often be reproduced using a bunch-to-bunch iterative map formalism. The coefficients that parameterize the map function are readily obtained by fitting to results from compute-intensive electron cloud simulations. This paper derives an analytic expression for the linear map coefficient that governs weak cloud behaviour from first principles. Good agreement is found when analytical results are compared with linear coefficient values obtained from numerical simulations. This analysis is useful in predicting thresholds beyond which electron cloud formation occurs, and thus in determining safety regions in parameter space where an accelerator can be operated without creating electron clouds. The formalism explicitly shows that the multipacting resonance condition is not a sine qua non for electron cloud formation.
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MOPCH134 |
Electron-impact Desorption at the RHIC Beam Pipes
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electron, injection, vacuum, BNL |
360 |
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- U. Iriso, U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- W. Fischer
BNL, Upton, Long Island, New York
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The electron induced molecular desorption coefficient of a material provides the number of molecules released when an electron hits its surface. This coefficient changes as a function of the material, energy of the electrons, surface status, etc. In this paper, this coefficient is inferred analyzing electron detector and pressure gauge signals during electron clouds at the Relativistic Heavy Ion Collider (RHIC) beam pipes. The evolution of the electron-impact desorption coefficient after weeks of electron bombardment is followed for both baked and unbaked stainless steel chambers, evaluating the feasibility of the scrubbing effect. Measurements of an energy spectrum during multipacting conditions are shown, and the final results are compared with laboratory simulations.
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MOPCH135 |
Benchmarking Electron Cloud Data with Computer Simulation Codes
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electron, simulation, LEFT, BNL |
363 |
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- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- G. Rumolo
CERN, Geneva
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Saturated electron flux and time decay of the electron cloud are experimentally inferred using many electron detector datasets at the Relativistic Heavy Ion Collider (RHIC). These results are compared with simulation results using two independent electron cloud computer codes, CSEC and ECLOUD. Simulation results are obtained over a range of different values for 1) the maximum Secondary Electron Yield (SEY), and 2) the electron reflection probability at zero energy. These results are used to validate parameterization models of the SEY as a function of the electron energy.
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MOPLS010 |
Measurement of Ion Beam Losses Due to Bound-free Pair Production in RHIC
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ion, LHC, luminosity, simulation |
553 |
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- J.M. Jowett, S.S. Gilardoni
CERN, Geneva
- R. Bruce
MAX-lab, Lund
- K.A. Drees, W. Fischer, S. Tepikian
BNL, Upton, Long Island, New York
- S.R. Klein
LBNL, Berkeley, California
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When the LHC operates as a Pb82+ ion collider, losses of Pb81+ ions, created through Bound-free Pair Production (BFPP) at the collision point, and localized in cold magnets, are expected to be a major luminosity limit. With Au79+ ions at RHIC, this effect is not a limitation because the Au78+ production rate is low, and the Au78+ beam produced is inside the momentum aperture. When RHIC collided Cu29+ ions, secondary beam production rates were lower still but the Cu28+ ions produced were predicted to be lost at a well-defined location, creating the opportunity for the first direct observation of BFPP effects in an ion collider. We report on measurements of localized beam losses due to BFPP with copper beams in RHIC and comparisons to predictions from tracking and Monte Carlo simulation.
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MOPLS021 |
Beam Pipe Desorption Rate in RHIC
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ion, electron, vacuum, beam-losses |
583 |
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MOPLS022 |
On the Feasibility of Polarized Heavy Ions in RHIC
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ion, resonance, proton, heavy-ion |
586 |
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- W.W. MacKay
BNL, Upton, Long Island, New York
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Heavy nonspherical ions such as uranium have been proposed for collisions in RHIC. When two such ions collide with their long axes aligned, then the plasma density might be as much as 60% higher. Since the collisions might have any orientation of the two nuclei, the alignment of the nuclei must be inferred from a complicated unfolding of multiplicity distributions. Instead, if it is possible to polarize the ions and control the orientation in RHIC, then a much better sensitivity could be obtained. This paper investigates the manipulation of such polarized ions with highly distorted shapes in RHIC. Several ion species are considered as possibilities with either full or partial Siberian snakes in RHIC.
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MOPLS023 |
Status of Fast IR Orbit Feedback at RHIC
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feedback, dipole, power-supply, injection |
589 |
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MOPLS024 |
RHIC Performance as Polarized Proton Collider in Run-6
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polarization, luminosity, emittance, AGS |
592 |
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- V. Ptitsyn, L. Ahrens, M. Bai, D.S. Barton, J. Beebe-Wang, M. Blaskiewicz, A. Bravar, J.M. Brennan, K.A. Brown, D. Bruno, G. Bunce, R. Calaga, P. Cameron, R. Connolly, T. D'Ottavio, J. DeLong, K.A. Drees, A.V. Fedotov, W. Fischer, G. Ganetis, H. Hahn, T. Hayes, H.-C. Hseuh, H. Huang, P. Ingrassia, D. Kayran, J. Kewisch, R.C. Lee, V. Litvinenko, A.U. Luccio, Y. Luo, W.W. MacKay, Y. Makdisi, N. Malitsky, G.J. Marr, A. Marusic, R.J. Michnoff, C. Montag, J. Morris, T. Nicoletti, B. Oerter, F.C. Pilat, P.H. Pile, T. Roser, T. Russo, J. Sandberg, T. Satogata, C. Schultheiss, S. Tepikian, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, A. Zaltsman, A. Zelenski, K. Zeno, S.Y. Zhang
BNL, Upton, Long Island, New York
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The Relativistic Heavy Ion Collider in Run-6 was operating in polarized proton mode. With two Siberian Snakes per ring, the polarized protons were brought into collisions at 100 Gev and 31.2 Gev energies. The control of polarization orientation at STAR and PHENIX experiments was done using helical spin rotators. Physics studies were conducted with longitudinal, vertical and radial beam polarization at collision points. This paper presents the performance of RHIC as a polarized proton collider in the Run-6 with emphasis on beam polarization and luminosity issues.
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MOPLS025 |
Experience in Reducing Electron Cloud and Dynamic Pressure Rise in Warm and Cold Regions in RHIC
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emittance, electron, proton, luminosity |
595 |
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- S.Y. Zhang, L. Ahrens, J.G. Alessi, M. Bai, M. Blaskiewicz, P. Cameron, R. Connolly, K.A. Drees, W. Fischer, J. Gullotta, P. He, H.-C. Hseuh, H. Huang, R.C. Lee, V. Litvinenko, W.W. MacKay, C. Montag, T. Nicoletti, B. Oerter, F.C. Pilat, V. Ptitsyn, T. Roser, T. Satogata, L. Smart, L. Snydstrup, S. Tepikian, P. Thieberger, D. Trbojevic, J. Wei, K. Zeno
BNL, Upton, Long Island, New York
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Significant improvement has been achieved for reducing electron cloud and dynamic pressure rise at RHIC over several years; however, there remain to be factors limiting luminosity. The large scale application of non-evaporable getter (NEG) coating in RHIC has been proven effective in reducing electron multipacting and dynamic pressure rise. This will be reported together with the study of the saturated NEG coatings. Since beams with increased intensity and shorter bunch spacing became possible in operation, the electron cloud effects on beam, such as the emittance growth,are an increasing concern. Observations and studies are reported. We also report the study results relevant to the RHIC electron cloud and pressure rise improvement, such as the effect of anti-grazing ridges on electron cloud in warm sections, and the effect of pre-pumping in cryogenic regions.
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TUXPA02 |
RHIC Operational Status and Upgrade Plans
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ion, electron, luminosity, proton |
905 |
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- W. Fischer
BNL, Upton, Long Island, New York
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Since 2000 RHIC has collided, at 8 energies, 4 combinations of ion species, ranging from gold ions to polarized protons, and including the collisions of deuterons with gold ions. During that time the heavy ion luminosity increased by 2 orders of magnitude, and the proton polarization in store reached 46% on average. Planned upgrades include the evolution to the Enhanced Design parameters by 2008, the construction of an Electron Beam Ion Source (EBIS) by 2009, the installation of electron cooling for RHIC II, and the implementation of the electron-ion collider eRHIC. We review the expected operational performance with these upgrades.
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Transparencies
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TUZBPA01 |
The ERL High Energy Cooler for RHIC
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electron, ERL, luminosity, emittance |
940 |
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- I. Ben-Zvi
BNL, Upton, Long Island, New York
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This talk will first briefly review high-energy electron cooling, including the recent results from Fermilab. The main empasis will be on describing the proposed electron-cooling device for RHIC, based on an Energy Recovery Linac. Finally, results from the prototype ERL will presented.
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Transparencies
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TUPLS125 |
Spin Transport from AGS to RHIC with Two Partial Snakes in AGS
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AGS, injection, extraction, dipole |
1795 |
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- W.W. MacKay, A.U. Luccio, N. Tsoupas
BNL, Upton, Long Island, New York
- J. Takano
RIKEN, Saitama
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The stable spin direction in the RHIC rings is vertical. With one or two strong helical Siberian snakes in the AGS, the stable spin direction at extraction is not vertical. Interleaved vertical and horizontal bends in the transport line between AGS and the RHIC rings also tend to tip the spin away from the vertical. In order to preserve polarization in RHIC, we examine several options to improve the matching of the stable spin direction during beam transfer from the AGS to each of the RHIC rings. While the matching is not perfect, the most economical method appears to be a lowering of the injection energy by one unit of G*gamma to 45.5.
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WEXFI02 |
Observation and Modeling of Electron Cloud Instability
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electron, KEK, LHC, proton |
1887 |
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WEPCH064 |
Fast Compensation of Global Linear Coupling in RHIC using AC Dipoles
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coupling, quadrupole, resonance, injection |
2071 |
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- F. Franchi
GSI, Darmstadt
- R. Calaga
BNL, Upton, Long Island, New York
- R. Tomas
CERN, Geneva
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Global linear coupling has been extensively studied in accelerators and several methods have been developed to compensate the coupling vector C using skew quadrupole families scans. However, scanning techniques can become very time consuming especially during the commissioning of an energy ramp. In this paper we illustrate a new technique to measure and compensate, in a single machine cycle, global linear coupling from turn-by-turn BPM data without the need of a skew quadrupole scan. The algorithm is applied to RHIC BPM data using AC dipoles and compared with traditional methods.
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WEPCH104 |
Observation of the Long-range Beam-beam Effect in RHIC and Plans for Compensation
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LHC, simulation, beam-losses, emittance |
2158 |
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- W. Fischer, R. Calaga
BNL, Upton, Long Island, New York
- U. Dorda, J.-P. Koutchouk, F. Zimmermann
CERN, Geneva
- A.C. Kabel
SLAC, Menlo Park, California
- J. Qiang
LBNL, Berkeley, California
- V.H. Ranjibar, T. Sen
Fermilab, Batavia, Illinois
- J. Shi
KU, Lawrence, Kansas
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At large distances the electromagnetic field of a wire is the same as the field produced by a bunch. Such a long-range beam-beam wire compensator was proposed for the LHC, and single beam tests with wire compensators were successfully done in the SPS. RHIC offers the possibility to test the compensation scheme with colliding beams. We report on measurements of beam loss measurements as a function of transverse separation in RHIC at injection, and comparisons with simulations. We present a design for a long-range wire compensator in RHIC.
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WEPCH138 |
Simulations of Long-range Beam-beam Interaction and Wire Compensation with BBTRACK
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simulation, LHC, luminosity, emittance |
2245 |
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- U. Dorda, F. Zimmermann
CERN, Geneva
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We present weak-strong simulation results for the effect of long-range beam-beam collisions in LHC, SPS, RHIC and DAFNE, as well as for proposed wire compensation schemes or wire experiments, respectively. In particular, we discuss details of the simulation model, instability indicators, the effectiveness of compensation, the difference between nominal and PACMAN bunches for the LHC, beam experiments, and wire tolerances. The simulations are performed with the new code BBTRACK.
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WEPLS097 |
Random Errors in Superconducting Dipoles
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LHC, dipole, multipole, simulation |
2601 |
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- B. Bellesia, E. Todesco
CERN, Geneva
- C. Santoni
Université Blaise Pascal, Clermont-Ferrand
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The magnetic field in a superconducting magnet is mainly determined by the position of the conductors. Hence, the main contribution to the random field errors comes from random displacement of the coil with respect to its nominal position. Using a Monte-Carlo method, we analyze the measured random field errors of the main dipoles of the LHC, Tevatron, RHIC and HERA projects in order to estimate the precision of the conductor positioning reached during the production. The method can be used to obtain more refined estimates of the random components for future projects.
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THOAFI03 |
Global and Local Coupling Compensation in RHIC using AC Dipoles
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coupling, quadrupole, dipole, sextupole |
2774 |
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THPCH027 |
An Experimental Proposal to Study Heavy-ion Cooling in the AGS due to Beam Gas or the Intrabeam Scattering
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ion, electron, AGS, scattering |
2838 |
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- D. Trbojevic, L. Ahrens, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, W.W. MacKay, G. Parzen, T. Roser
BNL, Upton, Long Island, New York
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Low emittance of not-fully-stripped gold(Z=79) Au+77 Helium-like ion beams from the AGS (Alternating Gradient Synchrotron) could be attributed to the cooling phenomenon due to inelastic intrabeam scattering [1]. The low emittance gold beams have always been observed at injection in the Relativistic Heavy Ion Collider (RHIC). There have been previous attempts to attribute the low emittance to a cooling due to the exchange of energy between ions during the inelastic intrabeam scattering. The Fano-Lichten theory[2] of electron promotion might be applied during inelastic collisions between helium like gold ions in the AGS. During collisions if the ion energy is large enough, a quasi-molecule could be formed, and electron excitation could occur. During de-excitation of electrons, photons are emitted and a loss of total bunch energy could occur. This would lead to smaller beam size. We propose to inject gold ions with two missing electrons into RHIC at injection energy and study the beam behavior with bunched and de-bunched beam, varying the RF voltage and the beam intensity. If the "cooling" is observed additional.
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THPCH078 |
Successful Bunched-Beam Stochastic Cooling in RHIC
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kicker, ion, pick-up, proton |
2967 |
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- J.M. Brennan, M. Blaskiewicz, F. Severino
BNL, Upton, Long Island, New York
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Stochastic Cooling of high energy and high frequency bunched beam has been demonstrated in RHIC at 100 GeV. Narrowing of the Schottky spectrum and shorting of the bunch length resulted from cooling the beam for 90 minutes. The purpose of the stochastic cooling is to counteract the fundamental limit of the luminosity lifetime of heavy ions in RHIC which is Intra-Beam Scattering. IBS drives transverse emittance growth and longitudinal de-bunching. The major components of the system have been tested with heavy ion and proton beams in previous runs in RHIC, demonstrating that the difficult challenges of high frequency bunched beam stochastic cooling can be overcome. The vexing problem of pollution of the Schottky spectrum by coherent components is solved with optimized filtering and high dynamic range low noise electronics. A set of 16 high-Q cavities is used to achieve adequate kicker voltage in the 5 to 8 GHz band. This technique exploits the bunched beam time structure to level the microwave power requirement and enables the use of solid state amplifiers to drive the kickers. Because RHIC did not operate with heavy ions in the FY06 run, the system was tested with specially prepared low intensity protons bunches of 2·109 particles.
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THPCH105 |
Summary of Coupling and Tune Feedback Results during RHIC Run 6, and Possible Implications for LHC Commissioning
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coupling, feedback, betatron, LHC |
3044 |
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- P. Cameron, A. Della Penna, L.T. Hoff, Y. Luo, A. Marusic, V. Ptitsyn, C. Schultheiss
BNL, Upton, Long Island, New York
- M. Gasior, O.R. Jones
CERN, Geneva
- C.-Y. Tan
Fermilab, Batavia, Illinois
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Efforts to implement tune feedback during the acceleration ramp in RHIC have been hampered by the effect of large betatron coupling, as well as by the large dynamic range required by transition crossing with ion beams. Both problems have been addressed, the first by implementation of continuous measurement of coupling using the phase-locked tune meter, and the second by the development of the direct diode detection analog front end. Performance with these improvements will be evaluated during the first days of RHIC Run 6 beam commissioning. With positive results, the possibility of implementing operational feedback control of tune and coupling during beam commissioning will be considered. After beam commissioning, chromaticity feedback will be explored as a part of the accelerator physics experimental program. We will summarize the results of these investigations, and discuss possible implications of these results for LHC commissioning.
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THPCH197 |
Analysis of Availability and Reliability in RHIC Operations
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controls, luminosity, ion, cryogenics |
3257 |
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- F.C. Pilat, P. Ingrassia, R.J. Michnoff
BNL, Upton, Long Island, New York
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RHIC has been successfully operated for five years as a collider for different species, ranging from heavy ions including gold and copper, to polarized protons. We present a critical analysis of reliability data for RHIC that not only identifies the principal factors limiting availability but also evaluates critical choices at design times and assess their impact on present machine performance. RHIC availability data are compared to similar high-energy colliders and synchrotron light sources. The critical analysis of operations data is the basis for studies and plans to improve RHIC machine availability beyond the 60% typical of high-energy collider.
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