Fast failures in the LHC and the future high luminosity LHC

Lindstrom, Bjorn Hans Filip; Belanger, Philippe; Bortot, Lorenzo; Denz, Reiner; Mentink, Matthias; Ravaioli, Emmanuele; Mateos, Felix Rodriguez; Schmidt, R.; Uythoven, Jan; Valette, Matthieu; Verweij, Arjan; Wiesner, Christoph; Wollmann, Daniel; Zerlauth, Markus

doi:10.1103/physrevaccelbeams.23.081001

Cited by 4 publications

(4 citation statements)

References 36 publications

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“…Particular concerns arise for the operation of crab-cavities [23] that will also be installed starting in 2025 and will be used in the HL-LHC. These new devices have the potential to excite failures with the rise time of a few LHC turns [24], as well as from the risk of dumping asynchronously the two HL-LHC beams, which triggers a transverse kick on the beam -4 - that circulates for longer times (see [25] for an overview of various possible effects for HL-LHC).…”

Section: Hel Specifications For Enhanced Beam Collimation 31 Motivations and Required Performancementioning

confidence: 99%

Hollow electron lenses for beam collimation at the High-Luminosity Large Hadron Collider (HL-LHC)

Redaelli¹,

Appleby²,

Bruce³

et al. 2021

J. Inst.

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Electrons lenses produce a high-intensity electron beam and have a variety of applications to circular hadron accelerators. Electron beams of different transverse cross sections and distributions may be designed, depending on the desired application, and they are produced and steered along the orbit of the hadron beam, overlapping with it for typical distances of a few meters before being deflected away and disposed of. Hollow electron beams find applications to high-intensity beam collimation for machines like the CERN Large Hadron Collider (LHC). Such devices can be integrated in a collimation system to improve the halo-cleaning performance through an active control of the halo dynamics: the annular distribution of the electrons excites resonantly the beam tails surrounding the beam core, while the core itself remains unperturbed, as ideally it only "sees" the field-free "hole" in the electron distribution. Hollow electron lenses are part of the upgrade baseline of the High-Luminosity project of the LHC (HL-LHC) and will be installed in the machine during a long shutdown in 2025-2027 to mitigate effects from beam losses so to improve the collimation system performance. This paper describes the hollow electron lens project within the HL-LHC collimation upgrade. K: Accelerator Applications; Accelerator modelling and simulations (multi-particle dynamics; single-particle dynamics); Accelerator Subsystems and Technologies; Beam dynamics Work supported by the HL-LHC project.

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Section: Hel Specifications For Enhanced Beam Collimation 31 Motivations and Required Performancementioning

confidence: 99%

Hollow electron lenses for beam collimation at the High-Luminosity Large Hadron Collider (HL-LHC)

Redaelli¹,

Appleby²,

Bruce³

et al. 2021

J. Inst.

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“…• During the CLIQ discharge, the net field integral induced by the secondary coils is zero. This means that in the case of a spurious CLIQ triggering, the particle beam passing through the magnet is not pushed out of its trajectory, which may otherwise cause severe damage to the particle accelerator [26].…”

Section: Overall Conceptmentioning

confidence: 99%

Secondary CLIQ, a robust, redundant, and cost-effective means of protecting high-field accelerator magnets

Mentink

Ravaioli

2020

Supercond. Sci. Technol.

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Secondary CLIQ is a quench protection method for protecting high-field accelerator magnets that involves charged capacitors into secondary normal-conducting coils that are magnetically coupled to the superconducting coils. The resulting coupling losses quickly brings the magnet to normal state and safely discharges it. No direct electrical or thermal link is required between the primary and secondary coils, and robust insulation is placed in between them. The two secondary circuits per magnet are galvanically insulated from the primary circuit, so that the tens to hundreds of CLIQ units needed to protect an accelerator circuit are galvanically insulated from one-another and from the superconducting magnets. The two secondary circuits per magnet each feature a CLIQ unit, and each CLIQ unit discharge is sufficient to bring the magnet to normal state over the entire operational current range. The coil geometry is such that the CLIQ discharge does not raise the voltage over the half-turns of the superconducting coils. After the superconducting coils develop resistance, a significant fraction of the stored magnetic energy is inductively transferred to and dissipated in the secondary coils. The resulting favourable adiabatic hot-spot temperature and voltage-to-ground enables the magnet designer to reduce the copper content of the superconducting coils, and thus lower the overall cost of the magnet. Secondary CLIQ quench simulations were performed on a hypothetical 14 m variant of the HD2 Nb3Sn dipole with a bore field of 16 T. It is demonstrated that the Secondary CLIQ method protects the magnet over its entire operational current range even in the case where one of the two CLIQ units fails to discharge with an adiabatic hotspot temperature of 248 K and voltage-to-ground of 610 V under nominal protection conditions, and a worst-case adiabatic hot-spot temperature of 263 K and voltage-to-ground of 840 V under fault conditions.

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“…During Run 2 of the LHC (2015-2018), it was recognized that the magnetic field generated during the discharge of the quench heaters can cause oscillations of the circulating beam [7]. Although this effect is not considered critical for the current LHC operation, the fast development of the orbit perturbation has triggered detailed studies to understand its criticality for High Luminosity (HL)-LHC operation [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…The orbit deviation after the quench heater firing, taking effect at turn 14, can clearly be observed. Since the quench heaters produce a horizontal dipole field, the beam is displaced in the vertical plane [7,8]. In contrast, a reduction of the main dipole field following the quench would displace the beam in the horizontal plane and would occur only on a time scale of tens of milliseconds.…”

Section: Introductionmentioning

confidence: 99%

Beam-based reconstruction of the shielded quench-heater fields for the LHC main dipoles

Richtmann

Bortot

Ravaioli

et al. 2023

J. Phys.: Conf. Ser.

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Small orbit oscillations of the circulating particle beams have been observed immediately following quenches in the LHC’s superconducting main dipole magnets. Magnetic fields generated during the discharge into the quench heaters were identified as the cause. Since the resulting, shielded field inside the beam screen cannot be measured in-situ, the time evolution of the field has to be reconstructed from the measured beam excursions. In this paper, the field-reconstruction method using rotation in normalized phase space and the optimized fitting algorithm are described. The resulting rise times and magnetic field levels are presented for quench events that occurred during regular operation as well as for dedicated beam experiments. Finally, different approaches to model the shielding behavior of the beam screen are discussed.

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Fast failures in the LHC and the future high luminosity LHC

Cited by 4 publications

References 36 publications

Hollow electron lenses for beam collimation at the High-Luminosity Large Hadron Collider (HL-LHC)

Hollow electron lenses for beam collimation at the High-Luminosity Large Hadron Collider (HL-LHC)

Secondary CLIQ, a robust, redundant, and cost-effective means of protecting high-field accelerator magnets

Beam-based reconstruction of the shielded quench-heater fields for the LHC main dipoles

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