Measurements of intra-beam scattering growth times with gold beam below transition in RHIC

Fischer, W.; Bai, Mei; Blaskiewicz, M.; Brennan, J.M.; Cameron, P.; Connolly, R.; Lehrach, A.; Parzen, G.; Tepikian, S.; Zeno, K.; Zeijts, J. van

doi:10.1109/pac.2001.987934

Cited by 10 publications

(9 citation statements)

References 6 publications

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“…Measurements of emittance growth at RHIC consistently show that the longitudinal emittance growth is consistent with IBS predictions, but the transverse emittances grow faster than expected [22,26].…”

Section: Need For Collimationsupporting

confidence: 62%

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The Crystal Collimation System of the Relativistic Heavy Ion Collider

Fliller¹

2004

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of the DissertationThe Crystal Collimation System of the Relativistic Heavy Ion Collider Crystal Channeling occurs when an ion enters a crystal with a small angle with respect to the crystal planes. The electrostatic interaction between the incoming ion and the lattice causes the ion to follow the crystal planes. By mechanically bending a crystal, it is possible to use a crystal to deflect ions. One novel use of a bent crystal is to use it to channel beam halo particles into a downstream collimator. By deflecting the halo particles into a collimator with a crystal it may be possible to improve the collimation efficiency as compared to a conventional two stage collimation system.A bent crystal was installed in the counterclockwise ring of the Relativistic Heavy Ion Collider (RHIC) prior to the FY2001 run to be used as the first stage of a two stage collimation system. We present a model and simulations to the predict crystal channeling efficiency. The simulations and model predict a channeling efficiency between 59% and 74% depending on the choice of optics.Attempts to reduce backgrounds in RHIC experiments using the crystal were unsuccessful because of the low channeling efficiency. Channeling results show a channeling efficiency 75% lower than originally predicted. Errors in the horizontal Twiss parameters at the crystal and inaccurate assumptions of the beam halo distribution are the cause of the large discrepancy. The strong scattering from the crystal made it impossible to intercept most of the scattered ions from the crystal using a single iii downstream absorber. Background at the STAR detector downstream of the crystal collimator was increased by as much as a factor of two and was rarely reduced below the uncollimated background rate. As a result, the crystal collimator was removed and the collimation system upgraded to a standard two stage system for the FY2004 gold -gold run.We also discuss the uses and effectiveness of the copper scrapers used during all RHIC runs. Measurements of diffusion rates and frequency analysis of beam losses were performed. These measurements aid in the understanding of beam growth rates.We performed beam profile measurements using the scrapers.The design and use of the upgraded collimation system is discussed. Future plans for collimation at RHIC are examined.

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Section: Need For Collimationsupporting

confidence: 62%

“…For a beam parallel to the crystal, ρ(x ) = δ(0), and the acceptance is 26) which in the harmonic approximation becomes…”

Section: Crystal Acceptancementioning

confidence: 99%

The Crystal Collimation System of the Relativistic Heavy Ion Collider

Fliller¹

2004

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“…3 shows a comparison between measured initial growth times and growth times computes with the IBS model. The difference in the longitudinal plane is about 50%, similar to the one achieved at injection [9]. Note that the transverse data have a large error.…”

Section: Intra-beam Scattering Computationssupporting

confidence: 78%

Beam lifetime and emittance growth measurements of gold beams in RHIC at storage

Fischer

Drees

Brennan

et al.

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)

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During stores of gold beams, longitudinal and transverse beam sizes were recorded. Longitudinal profiles were obtained with a wall current monitor. Transverse profiles were reconstructed from gold-gold collision rates at various relative transverse beam positions. The total beam lifetime was measured with a beam current transformer, the bunched beam lifetime with the wall current monitor. Diffusion rates in the beam halo were determined from the change in the loss rate when a scraper is retracted. The measurements are used to determine the lifetime limiting effects. Beam growth measurements are compared with computations of beam-growth times from intra-beam scattering.

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“…One of the statistical processes causing a spreading of particles in phase space or a continuous increase of beam emittance is the small angle multiple Coulomb scattering, called intrabeam scattering (IBS), which plays an important role in e þ =e − damping rings, high intensity/low energy light sources [25] and high intensity hadron [26] and ion [27] circular machines. The IBS theory for accelerators was firstly introduced by Piwinski [28] and extended by Martini [29], establishing a formulation called the standard Piwinski method.…”

Section: Intrabeam Scattering Theories Observations and Simulamentioning

confidence: 99%

Impact of non-Gaussian beam profiles in the performance of hadron colliders

Papadopoulou

Antoniou

Argyropoulos

et al. 2020

Phys. Rev. Accel. Beams

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At the Large Hadron Collider (LHC), the interplay between a series of effects, including intrabeam scattering (IBS), synchrotron radiation, longitudinal beam manipulations, two beam effects (beam-beam, e-cloud) and machine nonlinearities, can change the population of the core and tails and lead to non-Gaussian beam distributions, at different periods during the beam cycle. By employing generalized distribution functions, it can be demonstrated that the modified non-Gaussian beam profiles have an impact in the beam emittance evolution by itself and thereby to the collider luminosity. This paper focuses on the estimation of beam distribution modification and the resulting rms beam size due to the combined effect of IBS and synchrotron radiation by employing a Monte-Carlo simulation code which is able to track 3D generalized particle distributions (SIRE). The code is first benchmarked over classical semianalytical IBS theories and then compared with measurements from the LHC at injection and collision energies, including projections for the High-Luminosity LHC (HL-LHC) high brightness regime. The impact of the distribution shape on the evolution of the bunch characteristics and machine performance is finally addressed.

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Measurements of intra-beam scattering growth times with gold beam below transition in RHIC

Cited by 10 publications

References 6 publications

The Crystal Collimation System of the Relativistic Heavy Ion Collider

The Crystal Collimation System of the Relativistic Heavy Ion Collider

Beam lifetime and emittance growth measurements of gold beams in RHIC at storage

Impact of non-Gaussian beam profiles in the performance of hadron colliders

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