New approach to LHC optics commissioning for the nonlinear era

Maclean, Ewen; Tomás, Rogelio; Carlier, Felix Simon; Camillocci, Matteo Solfaroli; Dilly, Joschua; Portugal, J. Coello de; Fol, Elena; Fuchsberger, Kajetan; Valdivieso, Ana García-Tabarés; Giovannozzi, M.; Hofer, Michaël; Malina, Lukáš; Persson, Tobias; Skowroński, Piotr; Wegscheider, Andreas

doi:10.1103/physrevaccelbeams.22.061004

Cited by 15 publications

(18 citation statements)

References 26 publications

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“…Following Eq. (12), the transformation between normal form coordinates and Courant-Snyder coordinates reads…”

Section: A Particle Motion Under the Influence Of Couplingmentioning

confidence: 99%

“…This effect has been qualitatively demonstrated in [11] in simulations, where the impact of linear coupling on amplitude detuning is highlighted and how it may affect coherent instabilities in the LHC. Measurements of amplitude detuning are also used to establish corrections of nonlinear field errors in the triplet quadrupoles in the LHC [12]. Suboptimal correction of such may prove detrimental to beam lifetime and overall performance of the collider.…”

Section: Introductionmentioning

confidence: 99%

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Effect of local linear coupling on linear and nonlinear observables in circular accelerators

Hofer

Tomás

2020

Phys. Rev. Accel. Beams

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Operation of particle accelerators and correction of unavoidable magnet or alignment errors critically depend on the assessment of both global and local observables such as tune or resonance driving terms. With most of the observables being a sum of different error sources, careful disentangling is necessary in order to establish an optimal correction and allow for smooth operation. In the LHC, linear coupling has been proven to have a major impact on the beam dynamics and is taken to be one of the main sources of uncertainty when establishing corrections. In this paper an approach to evaluate the change of the Hamiltonian terms with linear coupling is presented. The validity of derived equations is demonstrated on a number of observables and benchmarked against simulations.

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“…Following Eq. (12), the transformation between normal form coordinates and Courant-Snyder coordinates reads…”

Section: A Particle Motion Under the Influence Of Couplingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of local linear coupling on linear and nonlinear observables in circular accelerators

Hofer

Tomás

2020

Phys. Rev. Accel. Beams

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“…For the β-beating contribution, the peak values have been used from Refs. [40][41][42]. For some cases the β-beating peak value is not reported in these references, in such cases the β-beating peak has been calculated as three times the β-beating RMS value.…”

Section: Reconstruction Of Physical Apertures From Physics Configurat...mentioning

confidence: 99%

Beam-based aperture measurements with movable collimator jaws as performance booster of the CERN Large Hadron Collider

et al. 2022

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The beam aperture of a particle accelerator defines the clearance available for the circulating beams and is a parameter of paramount importance for the accelerator performance. At the CERN Large Hadron Collider (LHC), the knowledge and control of the available aperture is crucial because the nominal proton beams carry an energy of 362 MJ stored in a superconducting environment. Even a tiny fraction of beam losses could quench the superconducting magnets or cause severe material damage. Furthermore, in a circular collider, the performance in terms of peak luminosity depends to a large extent on the aperture of the inner triplet quadrupoles, which are used to focus the beams at the interaction points. In the LHC, this aperture represents the smallest aperture at top-energy with squeezed beams and determines the maximum potential reach of the peak luminosity. Beam-based aperture measurements in these conditions are difficult and challenging. In this paper, we present different methods that have been developed over the years for precise beam-based aperture measurements in the LHC, highlighting applications and results that contributed to boost the operational LHC performance in Run 1 (2010–2013) and Run 2 (2015–2018)

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“…β-beating in the machine to the 2% level and the r.m.s. β Ã -beating down to the 1% level [1][2][3]. However, the continuous effort to reduce the beam sizes at the interaction points is starting to bring up the limitations of current optics measurements and correction methods.…”

Section: Introductionmentioning

confidence: 99%

New local optics measurements and correction techniques for the LHC and its luminosity upgrade

Portugal

Tomás

Hofer

2020

Phys. Rev. Accel. Beams

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As the beams at the interaction points (IPs) of circular colliders are pushed toward smaller sizes, the correction of the magnetic field errors in high-β regions become increasingly important, but also challenging. This paper presents an algorithm developed to compute automatically local corrections. This algorithm has been successfully used in the LHC and in simulations of the HL-LHC to establish tolerances for the magnetic errors. The limitations of the current β Ã measurement technique (K-modulation) are studied, together with alternative techniques for β Ã control: computing the minimum β near the IP using the betatron phase measured with new instrumentation and locating the beam waist via luminosity scans. This push toward smaller beam sizes also requires large β-functions in the arcs that enhance local errors currently negligible. Experimental results of a way of correcting this new type of local errors using orbit bumps in sextupoles is also presented. These studies forecast a drastic change in the LHC commissioning strategy to be applied in the HL-LHC for needing luminosity measurements in intermediate stages.

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New approach to LHC optics commissioning for the nonlinear era

Cited by 15 publications

References 26 publications

Effect of local linear coupling on linear and nonlinear observables in circular accelerators

Effect of local linear coupling on linear and nonlinear observables in circular accelerators

Beam-based aperture measurements with movable collimator jaws as performance booster of the CERN Large Hadron Collider

New local optics measurements and correction techniques for the LHC and its luminosity upgrade

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