Abstract
Modern hadron machines with high beam intensity may suffer from material damage in the case of large beam losses and even beam-intercepting devices, such as collimators, can be harmed. A systematic method to evaluate thresholds of damage owing to the impact of high energy particles is therefore crucial for safe operation and for predicting possible limitations in the overall machine performance. For this, a three-step simulation approach is presented, based on tracking simulations followed by calculations of energy deposited in the impacted material and hydrodynamic simulations to predict the thermomechanical effect of the impact. This approach is applied to metallic collimators at the CERN Large Hadron Collider (LHC), which in standard operation intercept halo protons, but risk to be damaged in the case of extraction kicker malfunction. In particular, tertiary collimators protect the aperture bottlenecks, their settings constrain the reach in ${\ensuremath{\beta}}^{*}$ and hence the achievable luminosity at the LHC experiments. Our calculated damage levels provide a very important input on how close to the beam these collimators can be operated without risk of damage. The results of this approach have been used already to push further the performance of the present machine. The risk of damage is even higher in the upgraded high-luminosity LHC with higher beam intensity, for which we quantify existing margins before equipment damage for the proposed baseline settings.
Highlights
Beam intercepting devices, such as collimators, are essential components for accelerators handling high-energy and high-intensity particle beams
Either during normal operation or from failures, must be tightly controlled through an effective strategy of collimator settings deployment in order to minimize the risk of damage for all machine equipment
As a general design principle, collimator settings and machine configurations are chosen with the aim to minimize the risk of beam losses beyond threshold 1
Summary
Beam intercepting devices, such as collimators, are essential components for accelerators handling high-energy and high-intensity particle beams. Tertiary collimators (TCT) provide local protection around the interaction points (IPs) They only intercept a small fraction of beam particles (order of 10−3 of the inelastic nuclear collisions in the TCP jaws) during standard operation. A simulation method to estimate damage thresholds for beam-intercepting devices is described and applied to various relevant LHC configurations to calculate the limits in terms of protons lost in the collimator jaws below which tungsten TCTs can operate safely without being damaged. Simulations of bunches of protons, where a realistic particle impact distribution on the collimators in the studied failure mode provides inputs for calculation of the energy deposited by the beam in the collimator.
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