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BEAM HALO FORMATION IN HIGH-INTENSITY BEAMS.

Description: Studies of beam halo became unavoidable feature of high-intensity machines where uncontrolled beam loss should be kept to extremely small level. For a well controlled stable beam such a loss is typically associated with the low density halo surrounding beam core. In order to minimize uncontrolled beam loss or improve performance of an accelerator, it is very important to understand what are the sources of halo formation in a specific machine of interest. The dominant mechanisms are, in fact, different in linear accelerators, circular machines or Energy Recovering Linacs (ERL). In this paper, we summarize basic mechanisms of halo formation in high-intensity beams and discuss their application to various types of accelerators of interest, such as linacs, rings and ERL.
Date: March 18, 2005
Creator: FEDOTOV, A. V.
Partner: UNT Libraries Government Documents Department

PROGRESS OF HIGH-ENERGY ELECTRON COOLING FOR RHIC.

Description: The fundamental questions about QCD which can be directly answered at Relativistic Heavy Ion Collider (RHIC) call for large integrated luminosities. The major goal of RHIC-I1 upgrade is to achieve a 10 fold increase in luminosity of Au ions at the top energy of 100 GeV/nucleon. Such a boost in luminosity for RHIC-II is achievable with implementation of high-energy electron cooling. The design of the higher-energy cooler for RHIC-II recently adopted a non-magnetized approach which requires a low temperature electron beam. Such electron beams will be produced with a superconducting Energy Recovery Linac (ERL). Detailed simulations of the electron cooling process and numerical simulations of the electron beam transport including the cooling section were performed. An intensive R&D of various elements of the design is presently underway. Here, we summarize progress in these electron cooling efforts.
Date: September 10, 2007
Creator: FEDOTOV,A.V.
Partner: UNT Libraries Government Documents Department

IBS and possible luminosity improvement for RHIC operation below transition energy

Description: There is a strong interest in low-energy RHIC collisions in the energy range below present RHIC transition energy. These collisions win help to answer one of the key questions in the field of QCD about the existence and location of a critical point on the QCD phase diagram. For such low-energy RHIC operation, particle losses from the RF bucket are of particular concern since the longitudinal beam size is comparable to the existing RF bucket at low energies. In this paper, we explore an Intrabeam Scattering (IBS) feature below transition energy that drives the transverse and longitudinal beam temperatures towards equilibrium to see whether we can minimize longitudinal diffusion due to IBS and predict some luminosity improvement for the low-energy RHIC project.
Date: May 4, 2009
Creator: Fedotov,A.V.
Partner: UNT Libraries Government Documents Department

SUMMARY OF BEAM COOLING AND INTRABEAM SCATTERING.

Description: For heavy-particle beams in storage rings where there is no significant synchrotron radiation damping, beam cooling is an essential tool in obtaining high phase-space density high brightness beams. Advances in various types of cooling such as electron, stochastic, laser and muon cooling are covered in dedicated Conferences. In this series of Workshops (HB2002-06), discussions are aimed only at a few specific subjects which are crucial for future projects. The discussion topics in our session closely followed those discussed during the HB2004 workshop [1]. Specifically, we concentrated on the topics of electron cooling and intrabeam scattering, motivated by the design of the future high-energy coolers [2,3,4]. These cooling projects at high-energy require accurate numerical modeling and experimental verification. A variety of tasks were put together at HB2004 [1]. In our working group we discussed a progress in addressing these tasks. We had 10 presentations [5]-[14] (with additional presentations in the joint sessions) which followed by dedicated discussions. Our main topics of discussions: intrabeam scattering (IBS), electron cooling, and beam stability are summarized.
Date: May 26, 2006
Creator: FEDOTOV, A.V.; MESHKOV, I.N. & WEI, J.
Partner: UNT Libraries Government Documents Department

Beam dynamics and expected RHIC performance with 56MHz RF upgrade

Description: An upgrade of the RHIC storage RF system with a superconducting 56 MHz cavity was recently proposed. This upgrade will provide a significant increase in the acceptance of the RHIC 197 MHz storage RF bucket. This paper summarizes simulations of beam evolution due to intra-beam scattering (IBS) for beam parameters expected with the 56 MHz SRF cavity upgrade. Expected luminosity improvements are shown for Au ions at 100 GeV/nucleon and protons at 250 GeV.
Date: May 4, 2009
Creator: Fedotov,A.V. & Ben-Zvi, I.
Partner: UNT Libraries Government Documents Department

ANALYSIS OF THE MAGNETIZED FRICTION FORCE.

Description: A comprehensive examination of theoretical models for the friction force, in use by the electron cooling community, was performed. Here, they present their insights about the models gained as a result of comparison between the friction force formulas and direct numerical simulations, as well as studies of the cooling process as a whole.
Date: May 29, 2006
Creator: FEDOTOV, A.V.; BRUHWILER, D.L. & SIDORIN, A.O.
Partner: UNT Libraries Government Documents Department

COOLING FORCE MEASUREMENTS IN CELSIUS.

Description: The design of future high energy coolers relies heavily on extending the results of cooling force measurements into new regimes by using simulation codes. In order to carefully benchmark these codes we have accurately measured the longitudinal friction force in CELSIUS by recording the phase shift between the beam and the RF voltage while varying the RF frequency. Moreover, parameter dependencies on the electron current, solenoid magnetic field and magnetic field alignment were carried out.
Date: September 18, 2005
Creator: GALNANDER, B.; FEDOTOV, A.V.; LITVINENKO, V.N. & AL., ET
Partner: UNT Libraries Government Documents Department

EXPERIMENTAL STUDIES OF IBS (INTRA-BEAM SCATTERING) IN RHIC AND COMPARISON WITH THEORY.

Description: A high-energy electron cooling system is presently being developed to overcome emittance growth due to Intra-beam Scattering (IBS) in RHIC. A critical item for choosing appropriate parameters of the cooler is an accurate description of the IBS. The analytic models were verified vs dedicated IBS measurements. Analysis of the 2004 data with the Au ions showed very good agreement for the longitudinal growth rates but significant disagreement with exact IBS models for the transverse growth rates. Experimental measurements were improved for the 2005 run with the Cu ions. Here, we present comparison of the 2005 data with theoretical models.
Date: May 29, 2006
Creator: FEDOTOV, A.V.; FISCHER, W.; TEPIKIAN, S. & WEI, J.
Partner: UNT Libraries Government Documents Department

HALF INTEGER RESONANCE CROSSING AND SPACE CHARGE LIMIT.

Description: We study the influence of space charge on the crossing of the second-order resonance and the associated space-charge limit in high-intensity rings. Two-dimensional simulation studies are compared and found to agree with the envelope models in the finding of an increased intensity limit due to the coherent frequency shift. We also discuss application of this effect to bunched beams and multi-turn injection painting, and the effect of high-order resonances and issues of the envelope instability.
Date: June 3, 2002
Creator: FEDOTOV,A.V. & HOFMAN,I.
Partner: UNT Libraries Government Documents Department

Halo formation in spheroidal bunches with self-consistent stationary distributions

Description: A new class of self-consistent 6-D phase space stationary distributions is constructed both analytically and numerically. The beam is then mismatched longitudinally and/or transversely, and the authors explore the beam stability and halo formation for the case of 3-D axisymmetric beam bunches using particle-in-cell simulations. They concentrate on beams with bunch length-to-width ratios varying from 1 to 5, which covers the typical range of the APT linac parameters. They find that the longitudinal halo forms first for comparable longitudinal and transverse mismatches. An interesting coupling phenomenon -- a longitudinal or transverse halo is observed even for very small mismatches if the mismatch in the other plane is large -- is discovered.
Date: December 31, 1998
Creator: Fedotov, A.V.; Gluckstern, R.L.; Kurennoy, S.S. & Ryne, R.D.
Partner: UNT Libraries Government Documents Department

EFFECT OF SPACE CHARGE ON STABILITY OF BEAM DISTRIBUTION IN THE SNS RING.

Description: In the Spallation Neutron Source (SNS) ring, multi-turn injection is employed to obtain a large transverse beam size which significantly reduces the space-charge tune shift of the accumulated beam. Careful choice of the painting scheme and bump function is required to obtain the desired beam profile together with low beam loss. In this paper we examine, both analytically and numerically, the effect of the space charge on the beam profile during multi-turn injection painting.
Date: June 18, 2001
Creator: FEDOTOV, A.V.; WEI, J. & GLUCKSTERN, R.L.
Partner: UNT Libraries Government Documents Department

EXCITATION OF RESONANCES DUE TO THE SPACE CHARGE AND MAGNET ERRORS IN THE SNS RING.

Description: The latest designs of high-intensity proton rings require minimal beam loss. The major cause of losses in a circular machine is the interplay of excited resonances, leading to particle diffusion. Such resonances could be driven by the space charge itself, magnet errors or a combined effect of the above. As a result, the goal of achieving low-level beam loss becomes especially challenging in the presence of both space charge and magnet imperfections. In this paper, we investigate the resonance excitation and their impact on the beam dynamics of the Spallation Neutron Source (SNS) ring, for various possible working points of the lattice.
Date: June 18, 2001
Creator: FEDOTOV, A.V.; MALITSKY, N.; PAPAPHILIPPOU, Y. & WEI, J.
Partner: UNT Libraries Government Documents Department

APPLICATION OF UAL TO HIGH INTENSITY BEAM DYNAMICS STUDIES IN THE SNS ACCUMULATOR RING.

Description: The SNS Ring off-line parallel simulation environment based on the Unified Accelerator Libraries (UAL) has been implemented and used for extensive full-scale beam dynamics studies arising in high-intensity rings. The paper describes the structure of this environment and its application to the development and analysis of the SNS accumulator ring beam loss model including a complex combination of several physical effects.
Date: June 3, 2002
Creator: MALITSKY,N.; FEDOTOV,A.V. & WEI,J.
Partner: UNT Libraries Government Documents Department

DETAILED STUDIES OF ELECTRON COOLING FRICTION FORCE.

Description: High-energy electron cooling for RHIC presents many unique features and challenges. An accurate estimate of the cooling times requires detailed simulation of the electron cooling process. The first step towards such calculations is to have an accurate description of the cooling force. Numerical simulations are being used to explore various features of the friction force which appear due to several effects, including the anisotropy of the electron distribution in velocity space and the effect of a strong solenoidal magnetic field. These aspects are being studied in detail using the VORFAL code, which explicitly resolves close binary collisions. Results are compared with available asymptotic and empirical formulas and also, using the BETACOOL code, with direct numerical integration of less approximate expressions over the specified electron distribution function.
Date: September 18, 2005
Creator: FEDOTOV, A. V.; BRUHWILER, D. L.; ABELL, D. T. & SIDORIN, A. O.
Partner: UNT Libraries Government Documents Department

NUMERICAL STUDIES OF THE FRICTION FORCE FOR THE RHIC ELECTRON COOLER.

Description: Accurate calculation of electron cooling times requires an accurate description of the dynamical friction force. The proposed RHIC cooler will require {approx}55 MeV electrons, which must be obtained from an RF linac, leading to very high transverse electron temperatures. A strong solenoid will be used to magnetize the electrons and suppress the transverse temperature, but the achievable magnetized cooling logarithm will not be large. In this paper, we explore the magnetized friction force for parameters of the RHIC cooler, using the VORPAL code [l]. VORPAL can simulate dynamical friction and diffusion coefficients directly from first principles [2]. Various aspects of the fiction force are addressed for the problem of high-energy electron cooling in the RHIC regime.
Date: May 16, 2005
Creator: FEDOTOV,A. V.; BEN-ZVI,I. & LITVINENKO, V.
Partner: UNT Libraries Government Documents Department

THE EFFECT OF MAGNETIC FIELD ERRORS ON DYNAMICAL FRICTION IN ELECTRON COOLERS.

Description: A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section [1], which would use -55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. A strong (1-5 T) solenoidal field will be used to magnetize the electrons and thus enhance the dynamical friction force on the ions. The physics of magnetized friction is being simulated for RHIC parameters [2,3,4], using the VORPAL code [5]. Most theoretical treatments for magnetized dynamical friction do not consider the effect of magnetic field errors, except in a parametric fashion. However, field errors can in some cases dramatically reduce the velocity drag and corresponding cooling rate. We present two simple analytical models for the magnetic field errors. The simulated dynamical friction for the case of a perfect solenoidal field is compared with results from these new models. We simulate parameters for the existing cooler of the CELSIUS ring, because recent experiments [6] provide data that will later be used for code validation.
Date: May 16, 2005
Creator: FEDOTOV, A. V. & LITVINENKO, V. N.
Partner: UNT Libraries Government Documents Department

COOLING DYNAMICS STUDIES AND SCENARIOS FOR THE RHIC COOLER.

Description: In this paper, we discuss various electron cooling dynamics studies for RHIC. We also present simulations [1] of various possibilities of using electron cooling at RHIC, which includes cooling at the top energy, pre-cooling at low energy, aspects of transverse and longitudinal cooling and their impact on the luminosity. Electron cooling at various collision energies both for heavy ions and protons is also discussed.
Date: May 16, 2005
Creator: FEDOTOV,A. V.; BEN-ZVI,I. & LITVINENKO, V.
Partner: UNT Libraries Government Documents Department

Interplay of space-charge and beam-beam effects in a collider

Description: Operation of a collider at low energy or use of cooling techniques to increase beam density may result in luminosity limitation due to the space-charge effects. Understanding of such limitation became important for Low-Energy RHIC physics program with heavy ions at the center of mass energies of 5-20 GeV/nucleon. For a collider, we are interested in a long beam lifetime, which limits the allowable space-charge tune shift. An additional complication comes from the fact that ion beams are colliding, which requires careful consideration of the interplay of direct space-charge and beam-beam effects. This paper summarizes the initial observations during experimental studies in RHIC at low energies.
Date: September 27, 2010
Creator: Fedotov, A.V.; Blaskiewicz, M.; Fischer, W.; Satogata, T. & Tepikian, S.
Partner: UNT Libraries Government Documents Department

ELECTRON COOLING SIMULATIONS FOR LOW-ENERGY RHIC OPERATION.

Description: Recently, a strong interest emerged in running the Relativistic Heavy Ion Collider (RHIC) at low beam total energies of 2.5-25 GeV/nucleon, substantially lower than the nominal beam total energy of 100 GeV/nucleon. Collisions in this low energy range are motivated by one of the key questions of quantum chromodynamics (QCD) about the existence and location of critical point on the QCD phase diagram. Applying electron cooling directly at these low energies in RHIC would result in significant luminosity increase and long beam stores for physics. Without direct cooling in RHIC at these low energies, beam lifetime and store times are very short, limited by strong transverse and longitudinal intrabeam scattering (IBS). In addition, for the lowest energies of the proposed energy scan, the longitudinal emittance of ions injected from the AGS into RHIC may be too big to fit into the RHIC RF bucket. An improvement in the longitudinal emittance of the ion beam can be provided by an electron cooling system at the AGS injection energy. Simulations of electron cooling both for direct cooling at low energies in RHIC and for injection energy cooling in the AGS were performed and are summarized in this report.
Date: September 10, 2007
Creator: FEDOTOV,A.V.; BEN-ZVI, I.; CHANG, X.; KAYRAN, D. & SATOGATA, T.
Partner: UNT Libraries Government Documents Department

DEVELOPMENT AND APPLICATIONS OF THE UAL BASED SNS RING SIMULATION ENVIRONMENT.

Description: The SNS Ring off-line parallel simulation environment based on the Unified Accelerator Libraries (UAL) has en implemented and used for extensive full-scale beam dynamics studies arising in high-intensity ring. The paper describes the structure of this environment and its application to various high-intensity topics and diagnostics modeling.
Date: April 8, 2002
Creator: MALITSKY,N.; CAMERON,P.; FEDOTOV,A.V.; SMITH,J. & WEI,J.
Partner: UNT Libraries Government Documents Department

EXPLORING TRANSVERSE BEAM STABILITY IN THE SNS IN THE PRESENCE OF SPACE CHARGE.

Description: The highest possible intensity in the machine is typically determined by the onset of coherent beam instabilities. Understanding the contribution of various effects to the damping and growth of such instabilities in the regime of strong space charge is thus of crucial importance. In this paper we explore transverse beam stability by numerical simulations using recently implemented models of transverse impedance and three-dimensional space charge. Results are discussed with application to the SNS accumulators.
Date: June 3, 2002
Creator: FEDOTOV,A.V.; BLASKIEWICZ,M.; WEI,J.; DANILOV,V.; HOLMES,J. & SHISHLO,A.
Partner: UNT Libraries Government Documents Department

EXPERIMENTAL BENCHMARKING OF THE MAGNETIZED FRICTION FORCE.

Description: High-energy electron cooling, presently considered as essential tool for several applications in high-energy and nuclear physics, requires accurate description of the friction force. A series of measurements were performed at CELSIUS with the goal to provide accurate data needed for the benchmarking of theories and simulations. Some results of accurate comparison of experimental data with the friction force formulas are presented.
Date: September 18, 2005
Creator: FEDOTOV, A. V.; GALNANDER, B.; LITVINENKO, V. N.; LOFNES, T.; SIDORIN, A. O.; SMIRNOV, A. V. et al.
Partner: UNT Libraries Government Documents Department

IBS FOR ION DISTRIBUTION UNDER ELECTRON COOLING.

Description: Standard models of the intra-beam scattering (IBS) are based on the growth of the rms beam parameters for a Gaussian distribution. As a result of electron cooling, the core of beam distribution is cooled much faster than the tails, producing a denser core. In this paper, we compare various approaches to IBS treatment for such distribution. Its impact on the luminosity is also discussed.
Date: May 16, 2005
Creator: FEDOTOV,A. V.; BEN-ZVI,I.; EIDELMAN, YU.; LITVINENKO, V. & PARZEN, G.
Partner: UNT Libraries Government Documents Department