RHIC

Paper	Title	Other Keywords	Page
MOPCH099	Performance and Capabilities of the NASA Space Radiation Laboratory at BNL	ion, booster, extraction, BNL	270
	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
	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.
MOPCH101	On the Feasibility of a Spin Decoherence Measurement	polarization, synchrotron, proton, AGS	276
	W.W. MacKay BNL, Upton, Long Island, New York
	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.
MOPCH102	A Straight Section Design in RHIC to Allow Heavy Ion Electron Cooling	electron, interaction-region, dipole, quadrupole	279
	D. Trbojevic, J. Kewisch, W.W. MacKay, T. Roser, S. Tepikian BNL, Upton, Long Island, New York
	The Relativistic Heavy Ion Collider (RHIC) has been continuously producing exciting results. One of the major luminosity limitations of the present collider is the intra beam scattering. A path towards the higher luminosities requires cooling of the heavy ion beams. Two projects in parallel electron and stochastic cooling are progressing very well. To allow interaction between electrons and the RHIC beams it is necessary to redesign one of the existing interaction regions in RHIC to allow for the longer straight section with fixed and large values of the betatron functions. We present a new design of the interaction region for the electron cooling in RHIC.
MOPCH132	Coupled Maps for Electron and Ion Clouds	electron, ion, simulation, proton	354
	U. Iriso CELLS, Bellaterra (Cerdanyola del Vallès) S. Peggs BNL, Upton, Long Island, New York
	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.
MOPCH133	An Analytic Calculation of the Electron Cloud Linear Map Coefficient	electron, simulation, LHC, heavy-ion	357
	U. Iriso CELLS, Bellaterra (Cerdanyola del Vallès) S. Peggs BNL, Upton, Long Island, New York
	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.
MOPCH134	Electron-impact Desorption at the RHIC Beam Pipes	electron, injection, vacuum, BNL	360
	U. Iriso, U. Iriso CELLS, Bellaterra (Cerdanyola del Vallès) W. Fischer BNL, Upton, Long Island, New York
	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.
MOPCH135	Benchmarking Electron Cloud Data with Computer Simulation Codes	electron, simulation, LEFT, BNL	363
	U. Iriso CELLS, Bellaterra (Cerdanyola del Vallès) G. Rumolo CERN, Geneva
	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.
MOPLS010	Measurement of Ion Beam Losses Due to Bound-free Pair Production in RHIC	ion, LHC, luminosity, simulation	553
	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
	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.
MOPLS021	Beam Pipe Desorption Rate in RHIC	ion, electron, vacuum, beam-losses	583
	H. Huang, W. Fischer, P. He, H.-C. Hseuh, U. Iriso, V. Ptitsyn, D. Trbojevic, J. Wei, S.Y. Zhang BNL, Upton, Long Island, New York
	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 250 meters of NEG coated beam pipes have been installed in many 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 experiment results are presented and analyzed in this paper.
MOPLS022	On the Feasibility of Polarized Heavy Ions in RHIC	ion, resonance, proton, heavy-ion	586
	W.W. MacKay BNL, Upton, Long Island, New York
	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.
MOPLS023	Status of Fast IR Orbit Feedback at RHIC	feedback, dipole, power-supply, injection	589
	C. Montag, J. Cupolo, J. Glenn, V. Litvinenko, A. Marusic, W. Meng, R.J. Michnoff, T. Roser, C. Schultheiss, J.E. Tuozzolo BNL, Upton, Long Island, New York
	To compensate modulated beam-beam offsets caused by mechanical vibrations of IR triplet quadrupoles at frequencies around 10 Hz, a fast IR orbit feedback system has been developed. We report design considerations and recent status of the system.
MOPLS024	RHIC Performance as Polarized Proton Collider in Run-6	polarization, luminosity, emittance, AGS	592
	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
	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.
MOPLS025	Experience in Reducing Electron Cloud and Dynamic Pressure Rise in Warm and Cold Regions in RHIC	emittance, electron, proton, luminosity	595
	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
	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.
TUXPA02	RHIC Operational Status and Upgrade Plans	ion, electron, luminosity, proton	905
	W. Fischer BNL, Upton, Long Island, New York
	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.
	Transparencies
TUZBPA01	The ERL High Energy Cooler for RHIC	electron, ERL, luminosity, emittance	940
	I. Ben-Zvi BNL, Upton, Long Island, New York
	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.
	Transparencies
TUPLS125	Spin Transport from AGS to RHIC with Two Partial Snakes in AGS	AGS, injection, extraction, dipole	1795
	W.W. MacKay, A.U. Luccio, N. Tsoupas BNL, Upton, Long Island, New York J. Takano RIKEN, Saitama
	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.
WEXFI02	Observation and Modeling of Electron Cloud Instability	electron, KEK, LHC, proton	1887
	K.C. Harkay ANL, Argonne, Illinois
	This presentation will review experimental results and the state of the art in the analysis and simulation of the electron cloud instability in hadron and positron storage rings.
	Transparencies
WEPCH064	Fast Compensation of Global Linear Coupling in RHIC using AC Dipoles	coupling, quadrupole, resonance, injection	2071
	F. Franchi GSI, Darmstadt R. Calaga BNL, Upton, Long Island, New York R. Tomas CERN, Geneva
	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.
WEPCH104	Observation of the Long-range Beam-beam Effect in RHIC and Plans for Compensation	LHC, simulation, beam-losses, emittance	2158
	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
	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.
WEPCH138	Simulations of Long-range Beam-beam Interaction and Wire Compensation with BBTRACK	simulation, LHC, luminosity, emittance	2245
	U. Dorda, F. Zimmermann CERN, Geneva
	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.
WEPLS097	Random Errors in Superconducting Dipoles	LHC, dipole, multipole, simulation	2601
	B. Bellesia, E. Todesco CERN, Geneva C. Santoni Université Blaise Pascal, Clermont-Ferrand
	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.
THOAFI03	Global and Local Coupling Compensation in RHIC using AC Dipoles	coupling, quadrupole, dipole, sextupole	2774
	R. Calaga BNL, Upton, Long Island, New York F. Franchi GSI, Darmstadt R. Tomas CERN, Geneva
	Compensation of transverse coupling during the RHIC energy ramp has been proven to be non-trivial and tedious. The lack of accurate knowledge of the coupling sources has initiated several efforts to develop fast techique using turn-by-turn BPM data to identify and compensate these sources. This paper aims to summarize the beam experiments performed to measure the coupling matrix and resonance driving terms with the aid of RHIC ac dipoles.
	Transparencies
THPCH027	An Experimental Proposal to Study Heavy-ion Cooling in the AGS due to Beam Gas or the Intrabeam Scattering	ion, electron, AGS, scattering	2838
	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
	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.
THPCH078	Successful Bunched-Beam Stochastic Cooling in RHIC	kicker, ion, pick-up, proton	2967
	J.M. Brennan, M. Blaskiewicz, F. Severino BNL, Upton, Long Island, New York
	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.
THPCH105	Summary of Coupling and Tune Feedback Results during RHIC Run 6, and Possible Implications for LHC Commissioning	coupling, feedback, betatron, LHC	3044
	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
	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.
THPCH197	Analysis of Availability and Reliability in RHIC Operations	controls, luminosity, ion, cryogenics	3257
	F.C. Pilat, P. Ingrassia, R.J. Michnoff BNL, Upton, Long Island, New York
	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.