The electron-cloud instability in PEP-II: an update

Furman, M.A.; Lambertson, G.

doi:10.1109/pac.1997.750777

Cited by 18 publications

(24 citation statements)

References 5 publications

(7 reference statements)

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“…It is well known that, for sufficiently high bunch currents, in a dipole field two vertical stripes of electron density, one on each side of the vertical (y) axis, occur at x locations where the electrons are within a certain distance range from the beam when the bunch appears. At this distance the beam kick produces electron energies near the peak of the secondary emission yield function [16][17][18]. If the bunch current of the beam is reduced the stripes will move closer to the y axis until they merge.…”

Section: A Orbits Of Electrons For Z Near the Maximal B Ymentioning

confidence: 99%

Electron cloud dynamics in the Cornell Electron Storage Ring Test Accelerator wiggler

Celata

2011

Phys. Rev. ST Accel. Beams

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The interference of stray electrons (also called ''electron clouds'') with accelerator beams is important in modern intense-beam accelerators, especially those with beams of positive charge. In magnetic wigglers, used, for instance, for transverse emittance damping, the intense synchrotron radiation produced by the beam can generate an electron cloud of relatively high density. In this paper the complicated dynamics of electron clouds in wigglers is examined using the example of a wiggler in the Cornell Electron Storage Ring Test Accelerator experiment at the Cornell Electron Storage Ring. Three-dimensional particle-in-cell simulations with the WARP-POSINST computer code show different density and dynamics for the electron cloud at locations near the maxima of the vertical wiggler field when compared to locations near the minima. Dynamics in these regions, the electron cloud distribution vs longitudinal position, and the beam coherent tune shift caused by the wiggler electron cloud will be discussed.

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Section: A Orbits Of Electrons For Z Near the Maximal B Ymentioning

confidence: 99%

Electron cloud dynamics in the Cornell Electron Storage Ring Test Accelerator wiggler

Celata

2011

Phys. Rev. ST Accel. Beams

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“…We have replaced the Poisson solver of the code POSINST [3][4][5][6], used in the computation of the electron cloud space-charge forces, by a multigrid-type solver that is much faster and more accurate than the old one. We have carefully tested the new solver in stand-alone mode, and we are confident that it gives correct (indeed, quite accurate) results.…”

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confidence: 99%

HINS R&D Collaboration on Electron Cloud Effects: MidyearReport

Furman¹,

Sonnad²,

Vay³

2006

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We present a report on ongoing activities on electron-cloud R&D for the MI upgrade. These results update and extend those presented in Refs. 1, 2. In this report we have significantly expanded the parameter range explored in bunch intensity N b , RMS bunch length σz and peak secondary emission yield (SEY) δmax, but we have constrained our simulations to a field-free region. We describe the threshold behaviors in all of the above three parameters. For δmax ≥ 1.5 we find that, even for N b = 1 × 10 11 , the electron cloud density, when averaged over the entire chamber, exceeds the beam neutralization level, but remains significantly below the local neutralization level (ie., when the electron density is computed in the neighborhood of the beam). This "excess" of electrons is accounted for by narrow regions of high concentration of electrons very close to the chamber surface, especially at the top and bottom of the chamber, akin to virtual cathodes. These virtual cathodes are kept in equilibrium, on average, by a competition between space-charge forces (including their images) and secondary emission, a mechanism that shares some features with the space-charge saturation of the current in a diode at high fields. For N b = 3 × 10 11 the electron cloud build-up growth rate and saturation density have a strong dependence on σz as σz decreases below ∼ 0.4 m, when the average electron-wall impact energy roughly reaches the energy Emax where δ peaks. We also present improved results on emittance growth simulations of the beam obtained with the code WARP/POSINST in quasi-static mode, in which the beam-(electron cloud) interaction is lumped into Ns "stations" around the ring, where Ns = 1, 2, . . . , 9. The emittance shows a rapid growth of ∼ 20% during the first ∼ 100 turns, followed by a much slower growth rate of ∼ 0.03%/turn. Concerning the electron cloud detection technique using microwave transmission, we present an improved dispersion relation for the TE mode of the microwaves, and a corresponding analytic estimate of the phase shift. I. ELECTRON CLOUD BUILD-UP.A. Remarks on the simulations.We have replaced the Poisson solver of the code POSINST [3][4][5][6], used in the computation of the electron cloud space-charge forces, by a multigrid-type solver that is much faster and more accurate than the old one. We have carefully tested the new solver in stand-alone mode, and we are confident that it gives correct (indeed, quite accurate) results. Owing to its inefficiency, the old solver could realistically be used only for very coarse grids, leading to intermittent problems at high N b and/or high δ max that sometimes crashed the code. For MI simulations, the improved code yields results only a few percent different from the old ones [1] for those cases in which the above-mentioned problem did not materialize. For other cases, notably the simulation of an LHC * Work supported by the FNAL HINS R&D Effort and by the US DOE under contract DE-AC02-05CH11231.† Electronic address: mafurman@lbl.gov; URL: http://mafurman. lbl.go...

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“…For the studies presented in this note we have used the simulation code POSINST [5][6][7][8]. We consider only two regions of the MI: a drift, and a dipole magnet of field B = 0.1 T, and we fix the beam energy at its injection value, E = 8 GeV.…”

Section: B Results For the Main Injectormentioning

confidence: 99%

“…In this article we present an examination of the EC at the MI by means of computer simulations with the code POSINST [5][6][7][8]. For the purposes of the present work, we fix two important parameters, namely the beam energy E at its injection value, and the peak value δ max of the secondary emission yield (SEY) of the vacuum chamber at 1.3.…”

Section: Introductionmentioning

confidence: 99%

A preliminary assessment of the electron cloud effect for the FNALmain injector upgrade

Furman¹

2005

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We present results from a preliminary assessment, via computer simulations, of the electroncloud density for the FNAL main injector upgrade at injection energy. Assuming a peak value for secondary emission yield δmax = 1.3, we find a threshold value of the bunch population, N b,th 1.25 × 10 11 , beyond which the electron-cloud density ρe reaches a steady-state level that is ∼ 10 4 times larger than for N b < N b,th , essentially neutralizing the beam, and leading to a tune shift ∼ 0.05. Our investigation is limited to a field-free region and to a dipole magnet region, both of which yield similar results for both N b,th and the steady-state value of ρe. Possible dynamical effects from the electron cloud on the beam, such as emittance growth and instabilities, remain to be investigated separately.

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The electron-cloud instability in PEP-II: an update

Cited by 18 publications

References 5 publications

Electron cloud dynamics in the Cornell Electron Storage Ring Test Accelerator wiggler

Electron cloud dynamics in the Cornell Electron Storage Ring Test Accelerator wiggler

HINS R&D Collaboration on Electron Cloud Effects: MidyearReport

A preliminary assessment of the electron cloud effect for the FNALmain injector upgrade

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