| Paper | Title | Page |
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| TUPS037 | Preliminary Assessment of Beam Impact Consequences on LHC Collimators | 1617 |
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| The correct functioning of the LHC collimation system is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, the robustness of the collimators plays an important role. An accident which causes the proton beam to hit a collimator might result in severe beam-induced damage and, in some cases, replacement of the collimator, with consequent downtime for the machine. In this paper, several case studies representing different realistic beam impact scenarios are shown. A preliminary analysis of the thermal response of tertiary collimators to beam impact is presented, from which the most critical cases can be identified. Such work will also help to give an initial insight on the operational constraints of the LHC by taking into account all relevant collimator damage limits. | ||
| TUPZ012 | Machine-induced Showers entering the ATLAS and CMS Detectors in the LHC | 1825 |
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| One source of experimental background in the LHC is showers induced by particles hitting the upstream collimators or particles that have been scattered on the residual gas. We estimate the flux and distribution of particles entering the ATLAS and CMS detectors through FLUKA simulations originating from tertiary collimator hits and inelastic beam-gas interactions. Comparisons to MARS results are also presented. | ||
| THPZ026 | Collimation Dependent Beam Lifetime and Loss Rates in the LHC | 3744 |
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| The four primary collimators in each LHC beam define the smallest aperture. Particles with high betatron amplitudes or momentum offset will therefore hit first a primary collimator. The instantaneous particle loss rate at primary collimators is an important measure for the global lifetime of the beams and a major ingredient to identify collimation induced performance limitations in the LHC. These loss rates have been measured during a number of LHC fills, featuring both "good" fills with high luminosity and "bad" fills with beam instabilities. The beam lifetime at the collimators was then calculated from this data for different cases. The results are presented and interpreted within this paper. | ||
| THPZ028 | Upgrade Studies for the LHC Collimators | 3750 |
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| The Phase-I LHC Collimation System has to be upgraded to work at high intensity and energy. Theoretical and engineering studies are focusing on different regions of the machine. The IR3 combined momentum and betatron cleaning, initially approved for installation, has presently been kept as fallback solution in case radiation to equipment limits LHC performance. The installation of collimators in the dispersion suppressor section DS3 has been delayed. In this paper we present predictions with matched optics and the effect of machine imperfections on the collimation performance with IR3 combined cleaning, with and without DS3 collimators. | ||
| THPZ030 | Halo Scrapings with Collimators in the LHC | 3756 |
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| The population of the beam halo has been measured in the LHC with beam scraping experiments. Primary collimators of the LHC collimation system were used to scrape the beam halo at different statuses of the machine (injection, top energy, separated and colliding beams). In addition these measurements were used to calibrate the beam loss monitor signals to loss rates at the primary collimators. Within this paper the halo scraping method, the measured halo distribution and the calibration factors are presented and compared to theoretical predictions. | ||
| THPZ032 | Evaluation of the Combined Betatron and Momentum Cleaning in Point 3 in Terms of Cleaning Efficiency and Energy Deposition for the LHC Collimation Upgrade | 3762 |
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Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program. The Phase I LHC Collimation System Upgrade could include moving part of the Betatron Cleaning from LHC Point 7 to Point 3 to improve both operation flexibility and intensity reach. In addition, the partial relocation of beam losses from the current Betatron cleaning region at Point 7 will mitigate the risks of Single Event Upsets to equipment installed in adjacent and partly not adequate shielded areas. A combined Betatron and Momentum Cleaning scenario at Point 3 implies the installation of new collimators and a new collimator aperture layout. This paper shows the whole LHC Collimator Efficiency variation with the new layout proposed at different beam energies. As part of the evaluation, energy deposition distribution in the IR3 region gives indications about the effect of this new implementation not only on the collimators themselves but also on the other beam line elements. |
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| THPZ035 | Comparison of LHC Collimation Setups with Manual and Semi-automatic Collimator Alignment | 3771 |
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| The LHC collimation system beam-based alignment procedure has recently been upgraded to a semi-automatic process in order to increase its efficiency. In this paper, we describe the parameters used to measure the accuracy, stability and performance of the beam-based alignment of the LHC collimation system. This is followed by a comparison of the results at 450 GeV and 3.5 TeV with (1) a manual alignment and (2) with the results for semi-automatic alignment. | ||
| THPZ027 | First Beam Results for a Collimator with In-jaw Beam Position Monitors | 3747 |
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| With more than 100 collimators the LHC has the most complex collimation system ever installed in an accelerator. The beam-based setup time of the system was a non-negligible factor during the commissioning of the LHC. In addition if the particle orbit at a collimator goes out of tolerance, this collimator needs to be setup again. To reduce the required setup time for the collimation system and to obtain the tight tolerances required for the LHC operation with small beta* and high beam energy, a new collimator design is being developed that integrates a beam position monitor (BPM) into the jaws of the collimator. A prototype of such a phase-II LHC collimator was installed in the SPS at CERN for the 2010 run. In this paper we present the first experimental results from the beam tests performed. | ||