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EXPERIMENTS WITH A DC WIRE IN RHIC

Description: A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanying simulations.
Date: June 25, 2007
Creator: FISCHER,W.; CALAGA, R.; DORDA, U.; KOUTCHOUK, J.-P.; ZIMMERMANN, F. & SEN, T.
Partner: UNT Libraries Government Documents Department

Coherent Beam-Beam Interactions in Electron-Positron Colliders

Description: We present the results of a new calculational technique that evaluates the beam-beam force due to an arbitrary charge distribution. We find coherent instabilities that dominate at certain operating points and depend strongly on the degree of damping in the system. We conclude that while these resonances may play a significant role for colliders with low damping, with a careful choice of operating points they should present no danger to the new generation of high luminosity heavy-quark factories under design.
Date: August 1, 1991
Creator: Krishnagopal, S.
Partner: UNT Libraries Government Documents Department

Beam-Beam Diagnostics from Closed-Orbit Distortion

Description: The authors study the applicability of beam-beam deflection techniques as a tuning tool for asymmetric B factories, focusing on PEP-II as an example. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, they calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the interaction point (IP), provide distinct signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed. Because of their two-ring structure, asymmetric B factories are likely to require more diagnostics and feedback mechanisms than single-ring colliders in order to guarantee head-on collisions. In addition to the traditional techniques, however, the independence of the two beams allows one to envisage other kinds of beam diagnostics. In this article they investigate one such possibility, by looking at the closed orbit distortion produced by the beam-beam interaction when the beams do not collide exactly head-on. They base this investigation on an analytic model and strong-strong multiparticle simulations. Although the discussion uses the PEP-II design as an example, the conclusion is that this technique is quite a promising diagnostics tool for asymmetric colliders in general.
Date: July 1, 1992
Creator: Furman, M.; Chin, Y.-H.; Eden, J.; Kozanecki, W.; Tennyson, J. & Ziemann, V.
Partner: UNT Libraries Government Documents Department

Studies of high luminosity, high disruption beam-beam interactions

Description: The e<sup>+</sup> e<sup>-</sup> linac-on-ring collider concept requires special attention due to the highly asymmetric nature of the beam-beam interaction. A brief review of recent studies is presented followed by some specific offset collision studies. Luminosity as a function of offset is also presented.
Date: February 1, 1991
Creator: Boyce, James
Partner: UNT Libraries Government Documents Department

Beam-Beam Compensation Activities at Fermilab. R&D Status.

Description: The beam-beam interaction in the Tevatron produces the betatron tune spread in each bunch and a bunch-to-bunch tune spread. The tune spread sets limits on bunch intensity and luminosity. The beam-beam e#11;ects for antiprotons are usually more severe since the proton bunch population is higher. The beam-beam e#11;ects for antiprotons can in principle be compensated with the use of an electron beam with a corresponding charge density. The status of studies of possibilities of the beam-beam compensation is reviewed in this paper.
Date: February 5, 1999
Creator: Sery, Andrey; Danilov, Slava; Finley, Dave & Shiltsev, Vladimir
Partner: UNT Libraries Government Documents Department

Experimental Studies of beam-beam effects in the Tevatron

Description: The long-range beam-beam interactions limit the achievable luminosity in the Tevatron. During the past year several studies ere performed on ways of removing the limitations at all stages of the operational cycle. The authors report here on some of these studies, including the effects of changing the helical orbits at injection and collision, tune and chromaticity scans and coupling due to the beam-beam interactions.
Date: June 9, 2003
Creator: al., Tanaji Sen et
Partner: UNT Libraries Government Documents Department

Tevatron beam-beam simulations at injection energy

Description: Major issues at Tevatron injection are the effects of 72 long-range beam-beam interactions together with the machine nonlinearity on protons and anti-protons. We look at particle tracking calculations of Dynamic Aperture (DA) under present machine conditions. Comparisons of calculations with observations and experiments are also presented in this report.
Date: May 28, 2003
Creator: Xiao, Meiqin; Erdelyi, Bela & Sen, Tanaji
Partner: UNT Libraries Government Documents Department

Numerical Simulation of Beam-Beam Effects in the Proposed Electron-Ion Colider at Jefferson Lab

Description: One key limiting factor to a collider luminosity is beam-beam interactions which usually can cause serious emittance growth of colliding beams and fast reduction of luminosity. Such nonlinear collective beam effect can be a very serious design challenge when the machine parameters are pushed into a new regime. In this paper, we present simulation studies of the beam-beam effect for a medium energy ring-ring electron-ion collider based on CEBAF.
Date: May 1, 2010
Creator: Balsa Terzic, Yuhong Zhang
Partner: UNT Libraries Government Documents Department

Summary of session 3 on synchrotron radiation and beam dynamics

Description: We summarize presentations, discussions and general conclusions of the Workshop session on 'Beam Dynamics Issues'. Major subjects include effects due to synchrotron radiation (SR), cryogenic loads, electron cloud, impedances, intra-beam scattering (IBS) and beam-beam interactions.
Date: December 1, 2010
Creator: Shiltsev, V.; /Fermilab; Metral, E. & /CERN
Partner: UNT Libraries Government Documents Department

Beam-Bem interactions

Description: In high energy storage-ring colliders, the nonlinear effect arising from beam-beam interactions is a major source that leads to the emittance growth, the reduction of beam life time, and limits the collider luminosity. In this paper, two models of beam-beam interactions are introduced, which are weak-strong and strong-strong beam-beam interactions. In addition, space-charge model is introduced.
Date: December 1, 2011
Creator: Kim, Hyung Jin
Partner: UNT Libraries Government Documents Department

Long-range and head-on beam-beam compensation studies in RHIC with lessons for the LHC

Description: Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are also important consideration for the LHC upgrades. To mitigate long-range effects current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. To reduce the head-on beam-beam effect electron lenses were proposed for both RIDC and the LHC. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: November 24, 2008
Creator: Fischer,W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Partner: UNT Libraries Government Documents Department

THE NEAR-INTEGER WORKING POINT FOR POLARIZED PROTONS IN THE RELATIVISTIC HEAVY ION COLLIDER

Description: To achieve the RHIC polarized proton enhanced luminosity goal of 150.10{sup 30} cm{sup -2}sec{sup -} on average in stores at 250 GeV, the luminosity needs to be increased by a factor of 3 compared to what was achieved in 2006. Since the number of bunches is already at its maximum of 1 1 1, limited by the injection kickers and the experiments' time resolution, the luminosity can only be increased by either increasing the bunch intensity and/or reducing the beam emittance. This leads to a larger beam-beam tuneshift parameter. Operations during 2006 has shown that the beam-beam interaction is already dominating the luminosity lifetime. To overcome this limitation, a near-integer working point is under study. We will present recent results of these studies.
Date: June 25, 2007
Creator: MONTAG,C.; BAI, M.; BEEBE-WANG, J.; CALAGA, R.; BLASKIEWICZ, M. & AL., ET
Partner: UNT Libraries Government Documents Department

TRANSVERSE BEAM TRANSFER FUNCTIONS OF COLLIDING BEAMS IN RHIC

Description: We use transverse beam transfer functions to measure tune distributions of colliding beams in RHIC. The tune has a distribution due to the beam-beam interaction, nonlinear magnetic fields -- particularly in the interaction region magnets, and non-zero chromaticity in conjunction with momentum spread. The measured tune distributions are compared with calculations.
Date: June 25, 2007
Creator: FISCHER,W.; BLASKIEWICZ, M.; CALAGA, R.; CAMERON, P.; HERR, W. & PIELONI, T.
Partner: UNT Libraries Government Documents Department

The effect of head-on beam-beam compensation on the stochastic boundaries and particle diffusion in RHIC.

Description: To compensate the effects from the head-on beam-beam interactions in the polarized proton operation in the Relativistic Heavy Ion Collider (RHIC), an electron lens (elens) is proposed to collide head-on with the proton beam. We used an extended version of SixTrack for multiparticle beam-beam simulation in order to study the effect of the e-lens on the stochastic boundary and also on diffusion. The stochastic boundary was analyzed using Lyapunov exponents and the diffusion was characterized as the increase in the rms spread of the action. For both studies the simulations were performed with and without the e-lens and with full and partial compensation. Using the simulated values of the diffusion an attempt to calculate the emittance growth rate is presented.
Date: June 23, 2008
Creator: Abreu,N.; Beebe-Wang, J.; FischW; Luo, Y. & Robert-Demolaize, G.
Partner: UNT Libraries Government Documents Department

EMITTANCE GROWTH DUE TO BEAM-BEAM EFFECT IN RHIC.

Description: The beam-beam interaction has a significant impact on the beam emittance growth and the luminosity lifetime in RHIC. A simulation study of the emittance growth was performed using the LIFETRAC code. The operational conditions of RHIC 2006 100GeV polarized proton run were used in the study. In this paper, the result of this study is presented and compared to the experimental measurements.
Date: June 25, 2007
Creator: BEEBE-WANG,J.
Partner: UNT Libraries Government Documents Department

Ion bunch length effects on the beam-beam interaction and its compensation in a high-luminosity ring-ring electron-ion collider

Description: One of the luminosity limits in a ring-ring electron-ion collider is the beam-beam effect on the electrons. In the limit of short ion bunches, simulation studies have shown that this limit can be significantly increased by head-on beam-beam compensation with an electron lens. However, with an ion bunch length comparable to the beta-function at the IP in conjunction with a large beam-beam parameter, the electrons perform a sizeable fraction of a betatron oscillation period inside the long ion bunches. We present recent simulation results on the compensation of this beam-beam interaction with multiple electron lenses.
Date: May 20, 2012
Creator: C., Montag; Oeftiger, A. & Fischer, W.
Partner: UNT Libraries Government Documents Department

Synchro-betatron effects in the presence of large Piwinski angle and crab cavities at the HL-LHC

Description: The reduction of {beta}* at the collision points for the high luminosity LHC (HL-LHC) requires an increment in the crossing angle to maintain the normalized beam separation to suppress the effects of long-range beam-beam interactions. However, an increase in the crossing angle may give rise to synchro-betatron resonances which may negatively affect the beam emittance and lifetime. 6D weak-strong and strong-strong simulations were performed to study the effect of synchro-betatron resonances in the context of the HL-LHC layout and its suppression via crab crossing.
Date: May 20, 2012
Creator: S., White; Calaga, R. & Miyamoto, R.
Partner: UNT Libraries Government Documents Department

Closed Orbit Distortion and the Beam-Beam Interaction

Description: We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed.
Date: February 23, 2007
Creator: Furman, M.; Chin, Y.; Eden, J.; /LBL, Berkeley; Kozanecki, W.; /DAPNIA, Saclay /SLAC et al.
Partner: UNT Libraries Government Documents Department

Recent Progress in a Beam-Beam Simulation Code for Circular Hadron Machines

Description: While conventional tracking codes can readily provide higher-order optical quantities and give an estimate of dynamic apertures, they are unable to provide directly measurable quantities such as lifetimes and loss rates. The particle tracking framework Plibb aims at modeling a storage ring with sufficient accuracy and a sufficiently high number of turns and in the presence of beam-beam interactions to allow for an estimate of these quantities. We provide a description of new features of the codes; we also describe a novel method of treating chromaticity in ring sections in a symplectic fashion.
Date: September 10, 2007
Creator: Kabel, Andreas; /SLAC; Fischer, Wolfram; /Brookhaven; Sen, Tanaji & /Fermilab
Partner: UNT Libraries Government Documents Department

Summary of the LARP Mini-Workshop on Beam-Beam Compensation 2007

Description: The LARP Mini-Workshop on Beam-Beam Compensation 2007 was held at SLAC, 2-4 July 2007. It was attended by 33 participants from 10 institutions in Asia, Europe, and America. 26 presentations were given, while more than one third of the time was allocated to discussions. The workshop web site is Ref. [1]. The workshop's main focus was on long-range and head-on beam-beam compensation, with a view towards application in the LHC. Other topics included the beam-beam performance of previous, existing and future circular colliders; beam-beam simulations; new operating modes, theory, and unexplained phenomena. This summary is also published as Ref. [2].
Date: November 7, 2011
Creator: Fischer, Wolfram; /Brookhaven; Bruning, Oliver S.; Koutchouk, J.P.; Zimmermann, F.; /CERN et al.
Partner: UNT Libraries Government Documents Department

Commisioning of the second Tevatron electron lens and beam study results

Description: In the framework of Fermilab's Beam-Beam Compensation (BBC) project, the 2nd Tevatron Electron Lens (TEL2) was installed in the Tevatron during Spring 2006 shutdown. It was successfully commissioned and a series of beam studies has been carried out in single bunch and all-bunch modes. The paper describes TEL2 commissioning and beam studies results.
Date: June 1, 2007
Creator: Kamerdzhiev, V.; Fellenz, B.; Hively, R.; Kuznetsov, G.; Olson, M.; Pfeffer, H. et al.
Partner: UNT Libraries Government Documents Department