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BEAM PIPE DESORPTION RATE IN RHIC.

Description: In the past, an increase of beam intensity in RHIC has caused several decades of pressure rises in the warm sections during operation. This has been a major factor limiting the RHIC luminosity. About 430 meters of NEG coated beam pipes have been installed in the warm sections to ameliorate this problem. Beam ion induced desorption is one possible cause of pressure rises. A series beam studies in RHIC has been dedicated to estimate the desorption rate of various beam pipes (regular and NEG coated) at various warm sections. Correctors were used to generate local beam losses and consequently local pressure rises. The experimental results are presented and analyzed in this paper.
Date: June 23, 2006
Creator: HUANG, H.; FISCHER, W.; HE, P.; HSEUH, H.C.; IRISO, U.; PTITSYN, V. et al.
Partner: UNT Libraries Government Documents Department

AN EXPERIMENTAL PROPOSAL TO STUDY HEAVY-ION COOLING IN THE AGS DUE TO BEAM GAS OR THE INTRABEAM SCATTERING.

Description: Low emittance of not-fully-stripped gold (Z=79) Au{sup +77} Helium-like ion beams from the AGS (Alternating Gradient Synchrotron) injector to the Relativistic Heavy Ion Collider (RHIC) could be attributed to the cooling phenomenon due to inelastic intrabeam scattering [1,2] or due to electron de-excitations from collisions with the residual gas [3]. 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 [4] of electron promotion might be applied during inelastic collisions between helium like gold ions in the AGS. The two K-shell electrons in gold Au{sup +77} could get promoted if the ions reach the critical distance of the closest approach during intra-beam scattering or collisions with the residual gas. During collisions if the ion energy is large enough, a quasi-molecule could be formed, and electron excitation could occur. During de-excitations 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 X-ray detectors could be installed to observe emitted photons.
Date: June 23, 2006
Creator: TRBOJEVIC, D.; AHERNS, L.; ROSER, T.; MACKAY, W.; BRENNAN, J.; BLASKIEWICZ,M. et al.
Partner: UNT Libraries Government Documents Department

Orbit, optics and chromaticity correction for PS2 negative momentum compaction lattices

Description: The effect of magnet misalignments in the beam orbit and linear optics functions are reviewed and correction schemes are applied to the negative momentum compaction lattice of PS2. Chromaticity correction schemes are also proposed and tested with respect to off-momentum optics properties. The impact of the correction schemes in the dynamic aperture of the lattice is finally evaluated.
Date: May 4, 2009
Creator: Papaphilippou,Y.; Barranco, J.; Bartmann, W.; Benedikt, M.; Carli, C.; de Maria, R. et al.
Partner: UNT Libraries Government Documents Department

Dynamic aperture evaluation for the RHIC 2009 polarized proton runs

Description: In this article we numerically evaluate the dynamic apertures of the proposed lattices for the coming Relativistic Heavy Ion Collider (RHIC) 2009 polarized proton (pp) 100 GeV and 250 GeV runs. One goal of this study is to find out the appropriate {beta}* for the coming 2009 pp runs. Another goal is to check the effect of second order chromaticity correction in the RHIC pp runs.
Date: May 4, 2009
Creator: Luo,Y.; Tepikain, S.; Bai, M.; Beebe-Wang, J.; Fischer, W.; Montag, c. et al.
Partner: UNT Libraries Government Documents Department

Linear optics design of negative momentum compaction lattices for PS2

Description: In view of the CERN Proton Synchrotron proposed replacement with a new ring (PS2), a detailed optics design has been undertaken following the evaluation of several lattice options. The basic arc module consists of cells providing negative momentum compaction. The straight section is formed with a combination of FODO and quadrupole triplet cells, to accommodate the injection and extraction systems, in particular the H{sup -} injection elements. The arc is matched to the straight section with a dispersion suppressor and matching module. Different lattices are compared with respect to their linear optics functions, tuning flexibility and geometrical acceptance properties.
Date: May 4, 2009
Creator: Papaphilippou,Y.; de Maria,R.; Barranco, J.; Bartmann, W.; Benedikt, M.; Carli, C. et al.
Partner: UNT Libraries Government Documents Department

DESIGN OF AN AC-DIPOLE FOR USE IN RHIC.

Description: We present two options for implementing a pair of AC-dipoles in RHIC for spin flipping, measuring linear optical functions and nonlinear diagnostics. AC-dipoles are magnets that can be adiabatically excited and de-excited with a continuous sine-wave in order to coherently move circulating beam out to large betatron amplitudes without incurring emittance blow up [1]. The AGS already uses a similar device for getting polarized proton beams through depolarizing resonances [2]. By placing the magnets in the IP4 common beam region, two AC-dipoles are sufficient to excite both horizontal and vertical motion in both RHIC rings. While we initially investigated an iron-dominated magnet design using available steel tape cores; we now favor a new air coil plus ferrite design featuring mechanical frequency tuning, in order to best match available resources to demanding frequency sweeping requirements. Both magnet designs are presented here along with model magnet test results. The challenge is to make AC-dipoles available for year 2000 RHIC running.
Date: March 29, 1999
Creator: PARKER,B.; BAI,M.; JAIN,A.; MCINTYRE,G.; METH,M.; PEGGS,S. et al.
Partner: UNT Libraries Government Documents Department

REAL-WORLD SORTING OF RHIC SUPERCONDUCTING MAGNETS.

Description: During the seven-year construction of the Relativistic Heavy Ion Collider (RHIC), more than 1700 superconducting dipoles, quadrupoles, sextupoles, and multi-layer correctors have been constructed and installed. These magnets have been sorted at several production stages to optimize their performance and reliability. For arc magnets, priorities have been put first on quench performance and operational risk minimization, second on field transfer function and other first-order quantities, and finally on nonlinear field errors which were painstakingly optimized at design. For Interaction-Region (IR) magnets, sorting is applied to select the best possible combination of magnets for the low-{beta}* interaction points (IP). This paper summarizes the history of this real-world sorting process.
Date: March 29, 1999
Creator: WEI,J.; GUPTA,R.; HARRISON,M.; JAIN,A.; PEGGS,S.; THOMPSON,P. et al.
Partner: UNT Libraries Government Documents Department

RHIC VERTICAL AC DIPOLE COMMISSIONING.

Description: The RHIC vertical ac dipole was installed in the summer of 2001. The magnet is located in the interaction region between sector 3 and sector 4 common to both beams. The resonant frequency of the ac dipole was first configured to be around half of the beam revolution frequency to act as a spin flipper. At the end of the RHIC 2002 run, the ac dipole frequency was reconfigured for linear optics studies. A 0.35 mm driven betatron oscillation was excited with the vertical ac dipole and the vertical betatron functions and phase advances at each beam position monitor (BPM) around the RHIC yellow ring were measured using the excited coherence. We also recorded horizontal turn-by-turn beam positions at each BPM location to investigate coupling effects. Analysis algorithms and measurement results are presented.
Date: June 2, 2002
Creator: BAI,M.; DELONG,J.; HOFF,L.; PAI,C.; PEGGS,S.; PIACENTINO,J. et al.
Partner: UNT Libraries Government Documents Department

COMMISSIONING OF THE RELATIVISTIC HEAVY ION COLLIDER.

Description: This report describes in detail steps performed in bringing the Relativistic Heavy Ion Collider (RHIC) from the commissioning into the operational stage when collisions between 60 bunches of fully striped gold ions, were routinely provided. Corrections of the few power supplies connections by the beam measurements are described. Beam lifetime improvements at injection, along the acceleration are shown. The beam diagnostic results; like Schottky detector, beam profile monitor, beam position monitors, tune meter and others, are shown [1].
Date: June 18, 2001
Creator: TRBOJEVIC,D.; AHRENS,L.; BLASKIEWICZ,M.; BRENNAN,M.; BAI,M.; CAMERON,P. et al.
Partner: UNT Libraries Government Documents Department

ELECTRON COOLING FOR RHIC.

Description: We introduce plans for electron-cooling of the Relativistic Heavy Ion Collider (RHIC). This project has a number of new features as electron coolers go: It will cool 100 GeV/nucleon ions with 50 MeV electrons; it will be the first attempt to cool a collider at storage-energy; and it will be the first cooler to use a bunched beam and a linear accelerator as the electron source. The linac will be superconducting with energy recovery. The electron source will be based on a photocathode gun. The project is carried out by the Collider-Accelerator Department at BNL in collaboration with the Budker Institute of Nuclear Physics.
Date: June 18, 2001
Creator: BEN-ZVI,I.; AHRENS,L.; BRENNAN,M.; HARRISON,M.; KEWISCH,J.; MACKAY,W. et al.
Partner: UNT Libraries Government Documents Department

Design of a non-scaling FFAG accelerator for proton therapy

Description: In recent years there has been a revival of interest in Fixed Field Alternating Gradient (FFAG) accelerators. In Japan a number have been built, or are under construction. A new non-scaling approach to the FFAG reduces the required orbit offsets during acceleration and the size of the required aperture, while maintaining the advantage of the low cost magnets associated with fixed fields. An advantage of the non-scaling FFAG accelerator, with respect to synchrotrons, is the fixed field and hence the possibility of high current and high repetition rate for spot scanning. There are possible advantages of the nonscaling design with respect to fixed-field cyclotrons. The non-scaling FFAG allows strong focusing and hence smaller aperture requirements compared to scaling designs, thus leading to very low losses and better control over the beam. We present, here, a non-scaling FFAG designed to be used for proton therapy.
Date: April 1, 2005
Creator: Trbojevic, D.; Ruggiero, A.G.; Keil, E.; Neskovic, N.; Belgrade, Vinca & Sessler, A.
Partner: UNT Libraries Government Documents Department

CRYSTAL COLLIMATION AT RHIC.

Description: For the year 2001 run, a bent crystal was installed in the yellow ring of the Relativistic Heavy Ion Collider (RHIC). The crystal forms the first stage of a two stage collimation system. By aligning the crystal to the beam, halo particles are channeled through the crystal and deflected into a copper scraper. The purpose is to reduce beam halo with greater efficiency than with a scraper alone. In this paper we present the first results from the use of the crystal collimator. We compare the crystal performance under various conditions, such as different particle species, and beta functions.
Date: June 2, 2002
Creator: FLILLER,III, R.P.; DREES,A.; GASSNER,D.; HAMMONS,L.; MCINTYRE,G.; PEGGS,S. et al.
Partner: UNT Libraries Government Documents Department

VACUUM PRESSURE RISE WITH INTENSE ION BEAMS IN RHIC.

Description: When RHIC is filled with bunches of intense ion beams a pressure rise is observed. The pressure rise exceeds the acceptable limit for operation with the design intensities. Observations of events leading to a pressure rise are summarized. Relevant parameters include ion species, charge per bunch, bunch spacing, and the location in the ring. Effects that contribute to a pressure rise are discussed, including beam gas ionization and ion desorption, loss-induced gas desorption, and electron desorption from electron clouds.
Date: June 2, 2002
Creator: FISCHER,W.; BAI,M.; BRENNAN,J.M.; BLASKIEWICZ,M.; CAMERON,P.; HSEUH,H.C. et al.
Partner: UNT Libraries Government Documents Department

COMMISSIONING OF RHIC AT 100 GEV / NUCLEON.

Description: This report describes commissioning of the Relativistic Heavy Ion Collider (RHIC) for 100 GeV/nucleon collisions at designed luminosity. To achieve these goals new systems had to be commissioned: Gamma-t transition crossing jump quadrupoles, rebucketing with the new RF storage cavities, phase lock loop feedback, betatron and crystal collimation, beta squeeze along the ramp, Siberian snake magnets for the proton polarization run, AC dipole system chromaticity measurements along the acceleration ramp, orbit correction, new ramp management system, upgraded sequencer, new data instrumentation and logger acquisition system etc.
Date: June 2, 2002
Creator: TRBOJEVIC,D.; AHRENS,L.; BLASKIEWICZ,M.; BRENNAN,J.M.; BAI,M.; CAMERON,P. et al.
Partner: UNT Libraries Government Documents Department

ELECTRON DETECTORS FOR VACUUM PRESSURE RISE DIAGNOSTICS AT RHIC.

Description: In the RHIC 2001 run, an unexpected vacuum pressure rise versus bunch increasing currents was observed in both gold and proton operations. This pressure increase due to molecular desorption is suspected to be induced mainly by electron multipacting, but other causes may coexist, such as ion desorption due to halo scraping. In order to get a reliable diagnostic of the phenomenon electron detectors have been installed along the RHIC ring. In this report we describe results measured by the electron detectors with energy filters during the RHIC 2002/2003 run.
Date: May 12, 2003
Creator: IRISO-ARIZ,U. DREES,A. FISCHER,W. GASSNER,D. GOULD,O. GULLOTTA,J. LEE,R. PONNAIYAN,V. TRBOJEVIC,D. ZENO,K. ZHANG,S. Y.
Partner: UNT Libraries Government Documents Department