Beam diffusion measurements using collimator scans in the LHC

Valentino, Gianluca; Aßmann, Ralph; Bruce, Roderik; Burkart, Florian; Previtali, V.; Redaelli, Stefano; Salvachua, Belen; Stancari, G.; Valishev, Alexander

doi:10.1103/physrevstab.16.021003

Cited by 21 publications

(32 citation statements)

References 7 publications

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“…This value is higher than the one deduced in Ref. [24] from measured halo diffusion coefficients (between 0.02 μm and 0.3 μm, depending on betatron amplitude and beam conditions). Nevertheless, the efficiency of the collimation system remains approximately the same and it is more efficient from the computing time point of view.…”

Section: B Beam Distributionscontrasting

confidence: 47%

Simulations of fast crab cavity failures in the high luminosity Large Hadron Collider

Yee-Rendón

López-Fernández

Barranco

et al. 2014

Phys. Rev. ST Accel. Beams

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Crab cavities (CCs) are a key ingredient of the high luminosity Large Hadron Collider (HL-LHC) project for increasing the luminosity of the LHC. At KEKB, CCs have exhibited abrupt changes of phase and voltage during a time period of the order of a few LHC turns and considering the significant stored energy in the HL-LHC beam, CC failures represent a serious threat in regard to LHC machine protection. In this paper, we discuss the effect of CC voltage or phase changes on a time interval similar to, or longer than, the one needed to dump the beam. The simulations assume a quasistationary-state distribution to assess the particles losses for the HL-LHC. These distributions produce beam losses below the safe operation threshold for Gaussian tails, while, for non-Gaussian tails are on the same order of the limit. Additionally, some mitigation strategies are studied for reducing the damage caused by the CC failures.

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Section: B Beam Distributionscontrasting

confidence: 47%

Simulations of fast crab cavity failures in the high luminosity Large Hadron Collider

Yee-Rendón

López-Fernández

Barranco

et al. 2014

Phys. Rev. ST Accel. Beams

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“…While for standard primary collimators this is not a critical parameter, as results are stable in a wide range of values up to hundreds of µm [35], for crystals the initial distribution affects significantly the channeling efficiency. Impact parameters of the order of tenths of a µm are expected in the real machine [36]. However, simulations with such low values would be not feasible due to the computing time needed.…”

Section: Simulation Setupmentioning

confidence: 99%

Design and implementation of a crystal collimation test stand at the Large Hadron Collider

et al. 2017

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Future upgrades of the CERN Large Hadron Collider (LHC) demand improved cleaning performance of its collimation system. Very efficient collimation is required during regular operations at high intensities, because even a small amount of energy deposited on superconducting magnets can cause an abrupt loss of superconducting conditions (quench). The possibility to use a crystal-based collimation system represents an option for improving both cleaning performance and impedance compared to the present system. Before relying on crystal collimation for the LHC, a demonstration under LHC conditions (energy, beam parameters, etc.) and a comparison against the present system is considered mandatory. Thus, a prototype crystal collimation system has been designed and installed in the LHC during the Long Shutdown 1 (LS1), to perform feasibility tests during the Run 2 at energies up to 6.5 TeV. The layout is suitable for operation with proton as well as heavy ion beams. In this paper, the design constraints and the solutions proposed for this test stand for feasibility demonstration of crystal collimation at the LHC are presented. The expected cleaning performance achievable with this test stand, as assessed in simulations, is presented and compared to that of the present LHC collimation system. The first experimental observation of crystal channeling in the LHC at the record beam energy of 6.5 TeV has been obtained in 2015 using the layout presented (Scandale et al., Phys Lett B 758:129, 2016). First tests to measure the cleaning performance of this test stand have been carried out in 2016 and the detailed data analysis is still on-going.

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“…A beam diffusion model for the LHC [10], based on the one developed for the Tevatron data [11,12], is able to accurately predict the BLM signal spike and decay. The particle loss rate at the collimator is equal to the flux at that location:…”

Section: B Loss Spike and Decaymentioning

confidence: 99%

Simulator for beam-based LHC collimator alignment

Valentino

Aßmann

Redaelli

et al. 2014

Phys. Rev. ST Accel. Beams

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In the CERN Large Hadron Collider, collimators need to be set up to form a multistage hierarchy to ensure efficient multiturn cleaning of halo particles. Automatic algorithms were introduced during the first run to reduce the beam time required for beam-based setup, improve the alignment accuracy, and reduce the risk of human errors. Simulating the alignment procedure would allow for off-line tests of alignment policies and algorithms. A simulator was developed based on a diffusion beam model to generate the characteristic beam loss signal spike and decay produced when a collimator jaw touches the beam, which is observed in a beam loss monitor (BLM). Empirical models derived from the available measurement data are used to simulate the steady-state beam loss and crosstalk between multiple BLMs. The simulator design is presented, together with simulation results and comparison to measurement data.

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Beam diffusion measurements using collimator scans in the LHC

Cited by 21 publications

References 7 publications

Simulations of fast crab cavity failures in the high luminosity Large Hadron Collider

Simulations of fast crab cavity failures in the high luminosity Large Hadron Collider

Design and implementation of a crystal collimation test stand at the Large Hadron Collider

Simulator for beam-based LHC collimator alignment

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