Final implementation, commissioning, and performance of embedded collimator beam position monitors in the Large Hadron Collider

et al. 2019

The Large Hadron Collider (LHC) at CERN is a 7 TeV proton synchrotron, with a design stored energy of 362 MJ per beam. The high-luminosity (HL-LHC) upgrade will increase this to 675 MJ per beam. In order to protect the superconducting magnets and other sensitive equipment from quenches and damage due to beam loss, a multi-level collimation system is needed. Detailed simulations are required to understand where particles scattered by the collimators are lost around the ring in a range of machine configurations. Merlin++ is a simulation framework that has been extended to include detailed scattering physics, in order to predict local particle loss rates around the LHC ring. We compare Merlin++ simulations of losses during the squeeze (the dynamic reduction of the β-function at the interaction points before the beams are put into collision) with loss maps recorded during beam squeezes for Run 1 and 2 configurations. The squeeze is particularly important as both collimator positions and quadrupole magnet currents are changed. We can then predict, using Merlin++, the expected losses for the HL-LHC to ensure adequate protection of the machine.

Section: Introductionmentioning

confidence: 99%

Performance of the Large Hadron Collider cleaning system during the squeeze: Simulations and measurements

Tygier

Appleby

et al. 2019

“…1 The computed BSC around the ring has to be compared to the minimum acceptable BSC above which it can be considered safe [38,[41][42][43]. The determination of the acceptable BSC involves the analysis of the performance of the collimation system that is supposed to intercept and dispose of high-amplitude particles [1,[45][46][47]. For HL-LHC at injection, the minimum BSC has been computed to 12.6σ based on studies of the halo distribution in various loss scenarios [42].…”

Section: Lattice and Optics Constraintsmentioning

confidence: 99%

Lattice and optics options for possible energy upgrades of the Large Hadron Collider

Keintzel

Tomás

et al. 2020

Studies of possible energy upgrades of the Large Hadron Collider (LHC) aim at increasing the current nominal beam energy of 7 TeV in view of expanding the discovery potential and physics reach of the LHC. Some critical aspects of the feasibility of partial or full energy upgrades are studied here, together with novel mitigation measures. Higher beam energies can be realized by pushing the installed main dipoles to their limits or by replacing different fractions of installed magnets. Moreover, a revised lattice design for a full energy upgrade, also known as the high-energy LHC (HE-LHC), is presented. The studies reported focus on the linear optics design and on the lattice layout. In particular, an optics with 60°transverse phase advance in the regular arc cells, meant to alleviate the strength requirements for the main quadrupoles, has been designed in view of possible beam tests during the next LHC run 3. The methods developed in this article, for matching the ring geometry to a reference tunnel, for improving the beam aperture, and for minimizing the required field strengths for new high-energy LHC-like machines, will also be applicable to other future circular collider projects.

“…The collimators of the betatron cleaning insertion in interaction region 7 (IR7) form the backbone of the multistage LHC collimation system [25][26][27][28][29][30]. All transverse halo particles with high betatron amplitudes should first hit a primary collimator (TCP) in IR7, installed in the horizontal, vertical, and skew planes.…”

Section: Lhc Beam Cleaningmentioning

confidence: 99%

Collimation-induced experimental background studies at the CERN Large Hadron Collider

Huhtinen

Manousos

et al. 2019

The data produced at the particle physics experiments at the Large Hadron Collider (LHC) contain not only the signals from the collisions, but also a background component from proton losses around the accelerator. Understanding, identifying and possibly mitigating this machine-induced background is essential for an efficient data taking, especially for some new physics searches. Among the sources of background are hadronic and electromagnetic showers from proton losses on nearby collimators due to beam-halo cleaning. In this article, the first dedicated LHC measurements of this type of background are presented. Controlled losses of a low-intensity beam on collimators were induced, while monitoring the backgrounds in the ATLAS detector. The results show a clear correlation between the experimental backgrounds and the setting of the tertiary collimators (TCTs). Furthermore, the results are used to show that during normal LHC physics operation the beam halo contributes to the total beam-induced background at the level of a percent or less. A second measurement, where the collimator positions are tightened during physics operation, confirms this finding by setting a limit of about 10% to the contribution from all losses on the TCTs, i.e. the sum of beam halo and elastic beam-gas scattering around the ring. Dedicated simulations of the halo-related background are presented and good agreement with data is demonstrated. These simulations provide information about features that are not experimentally accessible, like correlations between backgrounds and the distributions of proton impacts on the collimators. The results provide vital information about the dependence between background and collimator settings, which is of central importance when optimizing the LHC optics for maximum peak luminosity.