Slow emittance growth due to modulation effects in the presence of nonlinear fields

Brüning, O

doi:10.1063/1.45115

Cited by 5 publications

(7 citation statements)

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“…Typically, a few distinct frequencies feature much higher amplitudes and therefore, the focus of these studies was also to highlight the impact of a few distinct frequency lines. It was derived theoretically [8] as well as proven experimentally [4,5] that several frequencies in the noise spectrum are significantly more harmful than a single one. This knowledge was then applied to the LHC [11] and more recently to the HL-LHC [12][13][14] resulting in strict tolerances for the noise generated by the power converters.…”

Section: Introductionmentioning

confidence: 98%

“…All these magnets are installed at locations with high beta function and the beam is therefore particularly sensitive to any changes in the magnetic field of these magnets. The impact of the field fluctuations due to power supply noise, or the so called ripple, on the beam lifetime has been studied in the past in particular at the Super Proton Synchrotron (SPS) at CERN [4][5][6][7], the Hadron Electron Ring Facility (HERA) at DESY [8,9] and the TEVATRON at FERMILAB [10]. In the case of the SPS a tune ripple of 10 −4 turned out to be acceptable while experiences at HERA showed that a tune ripple of 10 −5 for low frequencies and 10 −4 for high frequencies could lead to a significant decrease in lifetime.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic frequency response of High-Luminosity Large Hadron Collider beam screens

Morrone

Martino

Maria

et al. 2019

Phys. Rev. Accel. Beams

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Magnetic fields used to control particle beams in accelerators are usually controlled by regulating the electrical current of the power converters. In order to minimize lifetime degradation and ultimately luminosity loss in circular colliders, current-noise is a highly critical figure of merit of power converters, in particular for magnets located in areas with high beta-function, like the High-Luminosity Large Hadron Collider (HL-LHC) insertions. However, what is directly acting upon the beam is the magnetic field and not the current of the power converter, which undergoes several frequency-dependent transformations until the desired magnetic field, seen by the beam, is obtained. Beam screens are very rarely considered when assessing or specifying the noise figure of merit, but their magnetic frequency response is such that they realize relatively effective low pass filtering of the magnetic field produced by the system magnet-power converter. This work aims at filling this gap by quantifying the expected impact of different beam screen layouts for the most relevant HL-LHC insertion magnets. A well-defined postprocessing technique is used to derive the frequency response of the different multipoles from multiphysics finite element method (FEM) simulation results. In addition, a wellapproximated analytical formula for the low-frequency range of multi-layered beam screens is presented.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Magnetic frequency response of High-Luminosity Large Hadron Collider beam screens

Morrone

Martino

Maria

et al. 2019

Phys. Rev. Accel. Beams

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“…The presence of two modulation frequencies led to a more rapid lifetime decrease and a shift of the chaotic boundary towards lower amplitudes. The increase of the losses and emittance growth was correlated with the overlap of multiple resonances [15]. The studies conducted in the Relativistic Heavy Ion Collider (RHIC) at BNL investigated the combined effect of synchrotron motion and power supply ripples on the Dynamic Aperture (DA) [16,17].…”

Section: Introductionmentioning

confidence: 99%

Tune modulation effects in the High Luminosity Large Hadron Collider

Kostoglou,

Bartosik,

Papaphilippou

et al. 2020

Preprint

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Several transverse noise sources, such as power supply ripples, can potentially act as an important limiting mechanism for the luminosity production of the Large Hadron Collider (LHC) and its future High-Luminosity upgrade (HL-LHC). In the presence of non-linearities, depending on the spectral components of the power supply noise and the nature of the source, such a mechanism can increase the diffusion of the particles in the distribution through the excitation of sideband resonances in the vicinity of the resonances driven by the lattice non-linearities. For the HL-LHC, due to the reduction of the beam size in the Interaction Points (IP) of the high luminosity experiments (IP1 and 5), increased sensitivity to noise effects is anticipated for the quadrupoles of the inner triplets. The modulation that may arise from the power supply ripples will be combined with the tune modulation that intrinsically emerges from the coupling of the transverse and longitudinal plane for off-momentum particles through chromaticity. To this end, the aim of this paper is to study the impact of tune modulation effects on the transverse beam motion resulting from the interplay between quadrupolar power supply ripples and synchro-betatron coupling. A power supply noise threshold for acceptable performance is estimated with single-particle tracking simulations by investigating the impact of different modulation frequencies and amplitudes on the Dynamic Aperture. The excitation of sideband resonances due to the modulation is demonstrated with frequency maps and the higher sensitivity to specific modulation frequencies is explained. Finally, a power supply noise spectrum consisting of several tones is considered in the simulations to determine whether the presence of power supply ripples in the quadrupoles of the inner triplet will limit the luminosity production in the HL-LHC era.

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“…Observations of harmonics of the mains power frequency in the beam spectrum have been reported in the past from several accelerators such as the Super Proton Synchrotron (SPS) at CERN [10][11][12][13][14], the Hadron-Electron Ring Accelerator (HERA) in Deutsches Elektronen-Synchrotron (DESY) [3,15,16], the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) [17,18] and the Tevatron in Fermi National Accelerator Laboratory (FNAL) [19,20]. The past studies can be roughly divided into two categories: observations of harmonics in the transverse beam spectrum, first, in the form of dipolar perturbations, i.e., the frequency of the lines does not depend on the tune and, second, as a tune modulation, with the harmonics appearing as sidebands around the betatron tune.…”

Section: Introductionmentioning

confidence: 99%

Origin of the 50 Hz harmonics in the transverse beam spectrum of the Large Hadron Collider

Kostoglou,

Arduini,

Intelisano

et al. 2020

Preprint

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Since the beginning of the Large Hadron Collider (LHC) commissioning, spectral components at harmonics of the mains frequency (50 Hz) have been observed in the transverse beam spectrum. This paper presents an overview of the most important observations, collected during the latest physics operation of the LHC in 2018, which clearly indicates that the harmonics are the result of a real beam excitation rather than an instrumental feature. Based on these findings, potential sources of the perturbation are discussed and a correlation with noise originating from the magnets' power converters is presented. As many of these tones reside in the vicinity of the betatron tune, they can increase the diffusion of the particles in the distribution in the presence of non-linear effects, leading to proton losses and eventually to a lifetime reduction. A quantitative characterization of the machine noise spectrum, together with an understanding of the noise source is an essential ingredient to evaluate the impact of the 50 Hz harmonics on the future upgrade of the LHC, the High Luminosity LHC (HL-LHC). To this end, simulations with the single-particle tracking code, SixTrack, are employed, including a realistic noise spectrum as extracted from experimental observations. The methods and results of the tracking studies are reported and discussed in this paper.

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Slow emittance growth due to modulation effects in the presence of nonlinear fields

Cited by 5 publications

References 0 publications

Magnetic frequency response of High-Luminosity Large Hadron Collider beam screens

Magnetic frequency response of High-Luminosity Large Hadron Collider beam screens

Tune modulation effects in the High Luminosity Large Hadron Collider

Origin of the 50 Hz harmonics in the transverse beam spectrum of the Large Hadron Collider

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