Linearized method for the study of transverse instabilities driven by electron clouds

Iadarola, Giovanni; Mether, Lotta; Mounet, Nicolas; Sabato, Luca

doi:10.1103/physrevaccelbeams.23.081002

Cited by 8 publications

(4 citation statements)

References 14 publications

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“…Introducing it for coasting beams, a new instability was revealed, the mode coupling instability for coasting beams, which was never discussed or described in the past [31][32][33][34] (see figure 23), and which revealed a plane exchange of the most critical instability vs. intensity (which was one of the important findings of the study). The detuning impedance has been also recently added in the Vlasov analysis with bunched beams (using also some simulation results), leading to an excellent agreement with the PyHEADTAIL macroparticle tracking code [35] (see also next section). The current challenge is to develop a fully self-consistent Vlasov solver for generalized impedances (without and with Landau damping).…”

Section: Jinst 16 P10009mentioning

confidence: 84%

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Wake field, impedance and collective instability

Métral¹

2021

J. Inst.

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The first mention of the impedance concept appeared on November 1966 in the CERN internal report Longitudinal instability of a coasting beam above transition, due to the action of lumped discontinuities by V.G. Vaccaro. Then, a more general treatment of it appeared in February 1967 in the CERN yellow report Longitudinal instabilities of azimuthally uniform beams in circular vacuum chambers of arbitrary electrical properties by A.M. Sessler and V.G. Vaccaro. The concept of wake field came two years later, in 1969, in the paper The wake field of an oscillating particle in the presence of conducting plates with resistive terminations at both ends by A.G. Ruggiero and V.G. Vaccaro. This was the beginning of many studies, which took place over the last five decades, and today, impedances and wake fields continue to be an important field of activity, as concerns theory, simulation, bench and beam-based measurements. Building a reliable impedance or wake field model of a machine is the first necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider), etc. Beam collective instabilities, and their mitigation, cover a wide range of effects in particle accelerators and they have been the subjects of intense research. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. With the increasing power of our computers this becomes easier but the need to continue and develop theories remains, to have a better understanding of the interplays between all these effects: the subject of impedance and beam instabilities in particle accelerators is far from being exhausted, as testified by the many new instability and stabilizing mechanisms which have been recently explained or discovered. Furthermore, in the context of the studies for possible future accelerators, some uncharted territories remain such as, for instance, the collective instabilities during the necessary ionization cooling for a muon collider.

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Section: Jinst 16 P10009mentioning

confidence: 84%

“…and the results were also compared against the conventional simulations based on the Particle-In-Cell method. The effect of transverse nonlinearities due to the electron cloud, which are neglected by the linearized method, were also analyzed [35].…”

Section: Jinst 16 P10009mentioning

confidence: 99%

Wake field, impedance and collective instability

Métral¹

2021

J. Inst.

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“…23), and which revealed a plane exchange of the most critical instability vs. intensity (which was one of the important findings of the study). The detuning impedance has been also recently added in the Vlasov analysis with bunched beams (using also some simulation results), leading to an excellent agreement with the PyHEADTAIL macroparticle tracking code [35] (see also next section). The current challenge is to develop a fully self-consistent Vlasov solver for generalized impedances (without and with Landau damping).…”

Section: Impedance-induced Instabilitiesmentioning

confidence: 84%

Wake field, impedance and collective instability

Métral

2021

Preprint

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Longitudinal instability of a coasting beam above transition, due to the action of lumped discontinuities" by V.G. Vaccaro. Then, a more general treatment of it appeared in February 1967 in the CERN yellow report "Longitudinal instabilities of azimuthally uniform beams in circular vacuum chambers of arbitrary electrical properties" by A.M. Sessler and V.G. Vaccaro. The concept of wake field came two years later, in 1969, in the paper "The wake field of an oscillating particle in the presence of conducting plates with resistive terminations at both ends" by A.G. Ruggiero and V.G. Vaccaro. This was the beginning of many studies, which took place over the last five decades, and today, impedances and wake fields continue to be an important field of activity, as concerns theory, simulation, bench and beam-based measurements. Building a reliable impedance or wake field model of a machine is the first necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider), etc. Beam collective instabilities, and their mitigation, cover a wide range of effects in particle accelerators and they have been the subjects of intense research. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. With the increasing power of our computers this becomes easier but the need to continue and develop theories remains, to have a better understanding of the interplays between all these effects: the subject of impedance and beam instabilities in particle accelerators is far from being exhausted, as testified by the many new instability and stabilizing mechanisms which have been recently explained or discovered. Furthermore, in the context of the studies for possible future accelerators, some uncharted territories remain such as, for instance, the collective instabilities during the necessary ionization cooling for a muon collider. K: Accelerator modelling and simulations (multi-particle dynamics, single-particle dynamics); Beam dynamics; Coherent instabilities.

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“…This method has been used very successfully in the CERN SPS for which the intensity threshold of the fast vertical instability at injection could be increased by a factor ∼ 2.5 as predicted by the simple scaling [28]. As transverse mode coupling instabilities can also be observed with beam-beam [29], electron cloud [30], or space charge [31], a similar mitigation method can be anticipated for these different cases (depending on the bunch length regime). For machines where transition crossing cannot be avoided, such as, for instance, in the CERN PS which was the first synchrotron where transition had to be crossed (which happened on November 24, 1959), a γ -transition jump is the only (known) method to overcome all the intensity limitations.…”

Section: Optics Manipulationsmentioning

confidence: 99%

General mitigation techniques for coherent beam instabilities in particle accelerators

Métral

2021

Eur. Phys. J. Plus

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An important number of coherent beam instability mechanisms can be observed in a particle accelerator, depending if the latter is linear or circular, operated at low, medium or high energy, with a small or a huge amount of turns (for circular machines), close to transition energy or not (below or above), with only one bunch or many bunches, with counter-rotating beams (such as in colliders) or not, if the beam is positively or negatively charged, if one is interested in the longitudinal plane or in the transverse plane, in the presence of linear coupling between the transverse planes or not, in the presence of nonlinearities or not, in the presence of noise or not, etc. Building a realistic impedance model of a machine is a necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics (linear and nonlinear), RF gymnastics, transverse damper, noise, space charge, electron cloud, and beam–beam (in a collider). Better characterising an instability is the first step before trying to find appropriate mitigation measures and push the performance of a particle accelerator, as some mitigation methods are beneficial for some effects and detrimental for some others. For this, an excellent instrumentation is of paramount importance to be able to diagnose if the instability is longitudinal or transverse, single bunch, or coupled bunch, involving only one mode of oscillation or several, and the evolution of the intrabunch motion with intensity is a fundamental observable with high-intensity high-brightness beams. Finally, among the possible mitigation methods of coherent beam instabilities, the ones perturbing the least the single-particle motion (leading to the largest necessary dynamic aperture and beam lifetime) and easiest to implement for day-to-day operation in the machine control room should be preferred.

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Linearized method for the study of transverse instabilities driven by electron clouds

Cited by 8 publications

References 14 publications

Wake field, impedance and collective instability

Wake field, impedance and collective instability

Wake field, impedance and collective instability

General mitigation techniques for coherent beam instabilities in particle accelerators

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