Space charge effects and coherent stability limits in barrier buckets

Hofmann, I.

doi:10.1103/physrevstab.6.034207

Cited by 7 publications

(7 citation statements)

References 15 publications

(15 reference statements)

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“…It is worth noting that saturating convective instabilities in the longitudinal plane are discussed for bunches with significant SC since long ago, see Ref. [19] and references therein. Although they are not intended to be considered in this paper, a simple explanation of their existence well deserves to be presented here.…”

Section: Absolute and Convective Instabilitiesmentioning

confidence: 99%

“…This presentation of the amplification indicates a slow convergence of the Fourier series for large amplification when the Fourier coefficients almost cancel each other in the denominator of Eq. (19). Thus, sufficiently many Fourier harmonics have to be kept to make the result correct; the higher amplification, the larger has to be the Fourier truncation number.…”

Section: Why Wrong Worked Rightmentioning

confidence: 99%

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Convective instabilities of bunched beams with space charge

Burov

2019

Phys. Rev. Accel. Beams

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For a single hadron bunch in a circular accelerator at zero chromaticity, without multi-turn wakes and without electron clouds and other beams, only one transverse collective instability is possible, the mode-coupling instability, or TMCI. For sufficiently strong space charge (SC), the instability threshold of the wake-driven coherent tune shift normally increases linearly with the SC tune shift, as independently concluded by several authors using different methods. This stability condition has, however, a very strange feature: at strong SC, it is totally insensitive to the number of particles. Thus, were it correct, such a beam with sufficiently strong SC, being stable at some intensity, would remain stable at higher intensity, regardless of how much higher! This paper suggests a resolution of this conundrum: while SC suppresses TMCI, it introduces head-to-tail convective amplifications, which could make the beam even less stable than without SC, even if all the coherent tunes are real, i.e. all the modes are stable in the conventional absolute meaning of the word. This is done using an effective new method of analysis of the beam's transverse spectrum for arbitrary space charge and wake fields. Two new types of beam instabilities are introduced: the saturating convective instability, SCI, and the absolute-convective instability, ACI.

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Section: Absolute and Convective Instabilitiesmentioning

confidence: 99%

Section: Why Wrong Worked Rightmentioning

confidence: 99%

Convective instabilities of bunched beams with space charge

Burov

2019

Phys. Rev. Accel. Beams

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“…Space charge below transition does not induce the microwave instability but some results, e.g. [6] suggest that it may moderate the growth of the instability. Simulations may be necessary to understand this process.…”

Section: Microwave Instabilitymentioning

confidence: 99%

“…Single particle dynamics within such a bucket was studied in [5]. Collective effects were numerically studied in the context of a low energy heavy ion ring [6]. Longitudinal stability in the Recycler may be influenced by several factors.…”

mentioning

confidence: 99%

Longitudinal Stability of Recycler Bunches; Part I: Thresholds for Loss of Landau Damping

Sen,

Bhat,

Ostiguy

2009

Preprint

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We examine the stability of intense flat bunches in barrier buckets used in the Recycler.We consider some common stationary distributions and show that they would be unstable against rigid dipole oscillations. We then discuss an analytical model for the line density that best describes measured bunch profiles. We include space charge in this model to predict the bunch intensity at which Landau damping would be lost. The dependence of this threshold on the bunch length is studied and related to the results of an experimental study with shorter bunch lengths. The threshold for the microwave instability is estimated. These studies will be followed by more detailed numerical studies.

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“…Significant theoretical as well as experimental research took place during the past two decades particularly due to its use in the Recycler Ring [9][10][11][12][13][14], induction accelerator at KEK [15], R&D effort at CERN and BNL [16] and the foreseen NESR facility at GSI [17]. The Recycler Ring at Fermilab is an 8 GeV proton/antiproton permanent magnet storage ring.…”

Section: Introductionmentioning

confidence: 99%

Pbar Beam Stacking in the Recycler by Longitudinal Phase-space Coating

Bhat

2013

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Barrier rf buckets have brought about new challenges in longitudinal beam dynamics of charged particle beams in synchrotrons and at the same time led to many new remarkable prospects in beam handling. In this paper, I describe a novel beam stacking scheme for synchrotrons using barrier buckets without any emittance dilution to the beam. First I discuss the general principle of the method, called longitudinal phase-space coating.Multi-particle beam dynamics simulations of the scheme applied to the Recycler, convincingly validates the concepts and feasibility of the method. Then I demonstrate the technique experimentally in the Recycler and also use it in operation. A spin-off of this scheme is its usefulness in mapping the incoherent synchrotron tune spectrum of the beam particles in barrier buckets and producing a clean hollow beam in longitudinal phase space. Both of which are described here in detail with illustrations. The beam stacking scheme presented here is the first of its kind.

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Space charge effects and coherent stability limits in barrier buckets

Cited by 7 publications

References 15 publications

Convective instabilities of bunched beams with space charge

Convective instabilities of bunched beams with space charge

Longitudinal Stability of Recycler Bunches; Part I: Thresholds for Loss of Landau Damping

Pbar Beam Stacking in the Recycler by Longitudinal Phase-space Coating

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