Collimation simulations for the FCC-ee Abramov, A.; Broggi, G.; Bruce, R. ...
Journal of instrumentation,
02/2024, Letnik:
19, Številka:
2
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Abstract
The collimation system of the Future Circular Collider,
operating with leptons (FCC-ee), must protect not only the
experiments against backgrounds, but also the machine itself from
beam ...losses. With a 17.8 MJ stored energy of the electron and
positron beams, they are highly destructive, and beam losses risk to
cause damage or a quench of superconducting elements. Accurate
collimation simulation tools and models are needed to design the
collimation system and optimize the collimation performance,
including magnetic tracking, synchrotron radiation and optics
tapering, as well as particle-matter interactions. As no existing
code was found that incorporated all these features, a new
simulation software tool has been developed. The tool is based on an
interface between a particle tracking engine, pyAT or Xtrack, and a
Monte-Carlo particle-matter interaction engine for collimator
scattering, BDSIM, which is based on Geant4. Results from a
simulation of edge scattering from a beam halo collimator in the
FCC-ee are presented to demonstrate the capabilities of the tool.
Simulation of beam–beam interaction with crab cavities for LHC upgrade Qiang, J.; Paret, S.; Ratti, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2018, Letnik:
900, Številka:
C
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The crab cavities are a critical component in the high luminosity LHC upgrade project to compensate the luminosity loss from large crossing angle collision. However, these crab cavities will not be ...perfect in the real accelerator. In this paper, we studied the effects of crab cavity imperfections on colliding beam luminosity lifetime degradation for the LHC upgrade through detailed numerical simulations. Our simulation results suggest that the white noise jitter in the crab cavity RF phase and voltage rms amplitudes should be kept below a few 10−5 for a good luminosity lifetime, while with frequency-dependent jitter, the amplitudes should be kept below a few 10−4 for a good lifetime. The RF multipole errors in the current crab cavity designs are small enough and would not cause extra luminosity degradation.
Beam Instabilities in Hadron Synchrotrons Metral, E.; Argyropoulos, T.; Bartosik, H. ...
IEEE transactions on nuclear science,
04/2016, Letnik:
63, Številka:
2
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Beam instabilities cover a wide range of effects in particle accelerators and they have been the subjects of intense research for several decades. 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. The aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.
Most hadron synchrotrons rely on lattice nonlinearities for Landau damping of impedance driven coherent modes of oscillation. However, in a collider, the presence of beam-beam interactions strongly ...modifies the transverse amplitude detuning and therefore the resulting stability diagram. A numerical tool to evaluate the effect of beam-beam on the stability diagram has been developed and is used to discuss observations during different phases of the operational cycle of the Large Hadron Collider during the 2012 proton run. In particular, we show the evolution of the stability diagram when the strength of long range beam-beam interactions is increased, during the betatron squeeze. Also, we investigate the stability of beams colliding with a small transverse offset and compare to observations of instabilities when bringing the beams into collision and while leveling the luminosity.
In high brightness circular colliders, coherent and incoherent beam dynamics are dominated by beam-beam interactions. It is generally assumed that the incoherent tune spread introduced by the ...beam-beam interactions is sufficiently large to cure any instabilities originating from impedance. However, as the two counterrotating beams interact they can give rise to coherent dipole modes and therefore modify the coherent beam dynamics and stability conditions. In this case, coherent beam-beam effects and impedance cannot be treated independently and their interplay should be taken into account in any realistic attempt to study the beam stability of colliding beams. Due to the complexity of these physics processes, numerical simulations become an important tool for the analysis of this system. Two approaches are proposed in this paper: a fully self-consistent multiparticle tracking including particle-in-cell Poisson solver for the beam-beam interactions and a linearized model taking into account finite bunch length effects. To ensure the validity of the results a detailed benchmarking of these models was performed. It will be shown that under certain conditions coherent beam-beam dipole modes can couple with higher order headtail modes and lead to strong instabilities with characteristics similar to the classical transverse mode coupling instability originating from impedance alone. Possible cures for this instability are explored both for single bunch and multibunch interactions. Simulation results and experimental evidences of the existence of this instability at the LHC will be presented for the specific case of offset collisions.
The Landau damping mechanism stabilizes the impedance driven head-tail modes in hadron synchrotrons. Because of the frequent coherent beam instabilities observed in the Large Hadron Collider in 2012, ...the Landau damping of the beams was doubted. Therefore, a transverse beam transfer function (BTF) system was installed in order to probe the transverse Landau damping of the beams and compare the measurements with expectations. The results of the BTF measurements acquired during several experiments in the LHC are summarized including different machine configurations. The method developed for the data analysis is described, and the comparison between the models and the measurements is also presented.
Luminosity scans for beam diagnostics Hostettler, M.; Fuchsberger, K.; Papotti, G. ...
Physical review. Accelerators and beams,
10/2018, Letnik:
21, Številka:
10
Journal Article
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A new type of fast luminosity separation scans (“emittance scans”) was introduced at the CERN Large Hadron Collider (LHC) in 2015. The scans were performed systematically in every fill with ...full-intensity beams in physics production conditions at the interaction point (IP) of the compact muon solenoid (CMS) experiment. They provide both transverse emittance and closed orbit measurements at a bunch-by-bunch level. The precise measurement of beam-beam closed orbit differences allowed a direct, quantitative observation of long-range beam-beam PACMAN effects, which agrees well with numerical simulations from an improved version of the TRAIN code.
In the frame of the FCC study we are designing a 27 TeV hadron collider in the LHC tunnel, called the High Energy LHC (HE-LHC). The HE-LHC can be realized by replacing the LHC's 8.33 T ...niobium-titanium dipole magnets with 16 T niobium-tin magnets developed for FCC-hh. A high-quality beam available from the upgraded LHC injector complex and significant radiation damping allow achieving the challenging target values for both peak and integrated luminosity required by particle physics. Tunnel integration determines the maximum outer size of the magnet cryAPCostat. The HE-LHC arc optics maximizes the dipole filling factor and optimizes the dynamic aperture, while limiting the field strengths of quadrupoles and sextupoles. The low-beta optics for the experimental insertions features a shielded quadrupole triplet even longer than the HL-LHC's, which can support an interaction-point beta function of 25 cm, and survive an integrated luminosity above 10/ab. Other challenges include collimation and extraction. The choice of injection energy and injector is another important element, and so are various collective effects. We here report the HE-LHC design status.
Recently, relations were established between the coefficients of free and forced amplitude detuning polynomial expansions. The forced oscillations were considered only in a single plane. In this ...paper we extend and generalize previous results by developing analytical equations that transform the free amplitude detuning function into the amplitude detuning involving forced oscillations in both transverse planes. These are used to obtain closed approximated formulas for the beam-beam amplitude detuning with forced oscillations. Formulas are compared to single and multiparticle simulations.
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