Multibunch and multiparticle simulation code with an alternative approach to wakefield effects

Migliorati, M.; Palumbo, L.

doi:10.1103/physrevstab.18.031001

Cited by 20 publications

(18 citation statements)

References 17 publications

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“…Here a more rigorous numerical study is performed with the help of the macroparticle tracking code PYHEADTAIL [24]. Some of the results have been benchmarked against other simulation codes which take into account collective effects [25][26][27]. For these studies, the vacuum chamber is assumed to be circular with 35 mm radius and three layers: a first layer of copper with 2 mm thickness, then 6 mm of dielectric and finally iron with resistivity ρ ¼ 10 −7 Ω m. It is also assumed to be coated with two different materials that in the following will be referred to as material A and material B with conductivities σ c;A ¼ 10 4 S=m and σ c;B ¼ 2 × 10 6 S=m, respectively.…”

Section: Single Bunch Beam Dynamicsmentioning

confidence: 99%

Impact of the resistive wall impedance on beam dynamics in the Future Circulare+e−Collider

Migliorati

Belli²,

Zobov

2018

Phys. Rev. Accel. Beams

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The Future Circular Collider study, which aims at designing post-LHC particle accelerator options, is entering in the final stage, which foresees a conceptual design report containing the basic requirements for a hadron and a lepton collider, as well as options for an electron-proton machine. Due to the high beam intensities of these accelerators, collective effects have to be carefully analyzed. Among them, the finite conductivity of the beam vacuum chamber represents a major source of impedance for the electron-positron collider. By using numerical and analytical tools, a parametric study of longitudinal and transverse instabilities caused by the resistive wall is performed in this paper for the case of the Future Circular Collider lepton machine, by taking into account also the effects of coating, used to fight the electron cloud build up. It will be proved that under certain assumptions the coupling impedance of a two layer system does not depend on the conductivity of the coating and this property represents an important characteristic for the choice of the material itself. The results and findings of this study have an impact on the machine design in several aspects. In particular the quite low threshold of single bunch instabilities with respect to the nominal beam current and the not negligible power losses due to the resistive wall are shown, together with the necessity of a new feedback system to counteract the fast transverse coupled bunch instability. The importance of a round vacuum chamber to avoid the quadrupolar tune shift is also discussed. Finally the crucial importance of the beam pipe material coating and thickness choice for the above results is underlined.

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Section: Single Bunch Beam Dynamicsmentioning

confidence: 99%

Impact of the resistive wall impedance on beam dynamics in the Future Circulare+e−Collider

Migliorati

Belli²,

Zobov

2018

Phys. Rev. Accel. Beams

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“…In the case of a resonator wake, the integration over history can be almost totally eliminated by 385 using invariance properties under translation of the resonator wake function [47], [48], [46]. The idea to express a general wakefield as a sum of resonators has been implemented recently by Migliorati and Palumbo in the tracking code MuSiC to simulate longitudinal multi-bunch effects [24], and in the most recent version of MBTRACK [27]. We plan to compare the computational efficiency of this method with our method based on a Taylor expansion in our future work on arbitrary wakefield effects.…”

Section: Discussionmentioning

confidence: 99%

Analysis of coupled-bunch instabilities for the NSLS-II storage ring with a 500 MHz 7-cell PETRA-III cavity

Bassi

Blednykh

Cheng

et al. 2016

Nuclear Instruments and Methods in Physics Research Section A:

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The NSLS-II storage ring is designed to operate with superconducting RF-cavities with the aim to store an average current of 500mA distributed in 1080 bunches, with a gap in the uniform filling for ion clearing. At the early stage of the commissioning (phase 1), characterized by a bare lattice without damping wigglers and without Landau cavities, a normal conducting 7-cell PETRA-III RF-cavity structure has been installed with the goal to store an average current of 25mA. In this paper we discuss our analysis of coupled-bunch instabilities driven by the Higher Order Modes (HOMs) of the 7-cell PETRA-III RF-cavity. As a cure of the instabilities, we apply a well-known scheme based on a proper detuning of the HOMs frequencies based upon cavity temperature change, and the use of the beneficial effect of the slow head-tail damping at positive chromaticity to increase the transverse coupled-bunch instability thresholds. In addition, we discuss measurements of coupled-bunch instabilities observed during the phase 1 commissioning of the NSLS-II storage ring. In our analysis we rely, in the longitudinal case, on the theory of coupled-bunch instability for uniform fillings, while in the transverse case we complement our studies with numerical simulations with OASIS, a novel parallel particle tracking code for self-consistent simulations of collective effects driven by short and long-range wakefields.the coupled-bunch instability for uniform fillings. A justification of this assumption is based on the work of Prabhakar [13] and Kohaupt [14]. A detailed analysis of the coupled-bunch instability driven by non-uniform fillings is discussed in a separate paper [15], where a derivation of the analytical formula for the complex frequency shift induced by arbitrary fillings is given and benchmarked against numerical simulations and measurements in the 15 NSLS-II storage ring. For the instability threshold calculations based on the HOMs of the 7-cell PETRA-III cavity structure we rely on the numerical data computed by R. Wanzenberg [16], complemented by measurements aimed to determine the dependence of the HOM frequencies on the cavity temperature [17]. In the longitudinal case, since in the NSLS-II storage ring the cut-off frequency of the PETRA-III cavity is higher than the case considered by R. Wanzenberg, we computed HOMs up to 1390 MHz [18], as shown in Table 2, with the GdfidL code [19]. 20 The beam dynamics simulation results discussed in this paper have been obtained with OASIS [20], a parallel code for self-consistent simulations of single and multi-bunch effects. For single-bunch effects, the code uses the same physical model of the TRANFT code developed by M. Blaskiewicz [21], [22], while in the case of multi-bunch effects the code implements a novel self-consistent algorithm to take into account long-range effects [23]. The novelty of the algorithm consists of the capability to simulate efficiently the self-consistent coupled-bunch interaction of 25 bunches with finite length distributed in arbitrary filling patterns, v...

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“…In order to better understand if the observed instability is of BBU kind, a simple simulation code has been developed. The code is based on the same approach as MuSiC [22] and does not use slices for the wakefield effects, as in PyHEADTAIL. It approximates the impedance with resonators, and it transports the wakefield from one particle to another using a matrix formalism.…”

Section: Review Of the Instability Mechanismmentioning

confidence: 99%

“…By following a formalism similar to that developed for the longitudinal case of Ref. [22], it is possible to obtain a transverse wakefield matrix, given by a single resonator, of the kind…”

Section: Appendix: Beam Break-up Simulation Codementioning

confidence: 99%

Instability studies at the CERN Proton Synchrotron during transition crossing

Migliorati¹,

Aumon

Koukovini-Platia

et al. 2018

Phys. Rev. Accel. Beams

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The CERN Proton Synchrotron (PS) routinely crosses transition energy at around 6 GeV in order to accelerate protons that are injected in the Super Proton Synchrotron (SPS) or transferred to users of fixed target experiments. Depending on the beam parameters and intensity, a fast vertical coherent instability occurs during transition crossing. The instability, characterized by beam losses and a frequency spectrum in the range of 500-900 MHz, represents an important intensity limitation for the neutron time-of-flight (nTOF) beam, and in general could represent a bottleneck for future high intensity beams. In order to better understand the nature and the source of the instability and to find possible mitigations, a dedicated measurement campaign took place. Parallel to the measurements, beam dynamics simulations have been performed to study the observed instability. In particular, single bunch effects have been simulated using the PS transverse beam coupling impedance model developed over recent years. In this paper we present the measurements results along with the obtained instability thresholds. Different beam configurations and stabilizing effects, such as the gamma jump scheme and the octupole-induced tune spread, are also considered. The measurements results are compared with simulations.

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Multibunch and multiparticle simulation code with an alternative approach to wakefield effects

Cited by 20 publications

References 17 publications

Impact of the resistive wall impedance on beam dynamics in the Future Circulare+e−Collider

Impact of the resistive wall impedance on beam dynamics in the Future Circulare+e−Collider

Analysis of coupled-bunch instabilities for the NSLS-II storage ring with a 500 MHz 7-cell PETRA-III cavity

Instability studies at the CERN Proton Synchrotron during transition crossing

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