| Paper | Title | Page |
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| MOYAA1 | Approaching the Nominal Performance at the LHC | 13 |
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| In 2015 the Large Hadron Collider (LHC) restarted for Run 2 after an almost two year long shutdown to consolidate the machine for operation at nominal beam energy. Following a month of recommissioning and training of the magnet system, the LHC operated for the first time at an energy of 6.5 TeV. The aim of this first year was to master operation at the higher energy and with beams of 25 ns spacing. In 2016 the performance could be pushed based on the experience of 2015, culminating with a luminosity 40% above the design value of 1034 cm-2s−1. The status of the machine operation, performance and prospects for the rest of Run 2 and Run 3 will be discussed. | ||
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Slides MOYAA1 [4.639 MB] | |
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOYAA1 | |
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| TUOCB1 | Progress in the Design of Beam Optics for FCC-ee Collider Ring* | 1281 |
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| The beam optics for the FCC-ee collider has been updated: (a) the layout is adjusted to a new footprint of FCC-hh, (b) the design around the interaction point is refined considering a number of machine-detecor interface issues, (c) the arc lattice is refined taking realistic magnet designs into account, (d) the β* and betatron tunes are re-optimized according to recent results of the beam-beam simulations, and more. These changes make the collider design more realistic without performance degradation. | ||
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Slides TUOCB1 [4.891 MB] | |
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUOCB1 | |
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| TUPVA005 | Impact of the Crossing Angle on Luminosity Asymmetries at the LHC in 2016 Proton Physics Operation | 2035 |
| SUSPSIK001 | use link to see paper's listing under its alternate paper code | |
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| During 2016 proton physics operation at the CERN Large Hadron Collider (LHC), an asymmetry of up to 10% was observed between the luminosities measured by the ATLAS and CMS experiments. As the same bunch pairs collide in both experiments, a difference in luminosities must be of either geometric or instrumental origin. This paper quantifies the impact of the crossing angle on this asymmetry. As the beams cross in different planes in the two experiments, non-round beams are expected to yield an asymmetry due to the crossing angle. Results from crossing angle measurements at both experiments are also shown and the impact on the luminosities is evaluated. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA005 | |
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| TUPVA014 | The 2016 Proton-Nucleus Run of the LHC | 2071 |
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| For five of the LHC experiments the second p-Pb collision run planned in 2016 offered the opportunity to answer a range of important physics questions arising from the surprise discoveries (e.g., flow-like collective phenomena in small systems) made in earlier Pb-Pb, p-Pb and p-p runs. However the diversity of the physics and their respective capabilities led them to request very different operating conditions, in terms of collision energy, luminosity and pile-up. These appeared mutually incompatible within the available one month of operation. Nevertheless, a plan to satisfy most requirements was developed and implemented successfully. It exploited different beam lifetimes at two beam energies of 4 Z TeV and 6.5 Z TeV, a variety of luminosity sharing and bunch filling schemes, and varying beam directions. The outcome of this very complex strategy for repeated re-commissioning and operation of the LHC included the longest ever LHC fill with luminosity levelled for almost 38 h. The peak luminosity achieved exceeded the design value by a factor 7.8 and integrated luminosity substantially exceeded the experiments' requests. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA014 | |
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| TUPVA025 | Observations of Beam Losses at the LHC During Reduction of Crossing Angle | 2105 |
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| Several machine development studies have been performed in 2016 at the LHC in order to evaluate the effects of reducing the crossing angles in favor of defining the maximum achievable luminosity in the ATLAS and CMS experiments. At the end of the LHC proton-proton run at 6.5TeV the reduction of the crossing angle from 185urad to 140urad was operationally implemented. The observation of beam losses and lifetimes during this process are analysed and discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA025 | |
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| TUPVA128 | Performance of the CERN Injector Complex and Transmission Studies into the LHC during the Second Proton-Lead Run | 2395 |
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| The LHC performance during the proton-lead run in 2016 fully relied on a permanent monitoring and systematic improvement of the beam quality in all the injectors. The beam production and characteristics are explained in this paper, together with the improvements realized during the run from the source up to the flat top of the LHC. Transmission studies from one accelerator to the next as well as beam quality evolution studies during the cycle at each accelerator, have been carried out and are summarized in this paper. In 2016, the LHC had to deliver the beams to the experiments at two different energies, 4 Z TeV and 6.5 Z TeV. The properties of the beams at these two energies are also presented | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA128 | |
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| WEPIK030 | Experimental Validation of the Achromatic Telescopic Squeezing Scheme at the LHC | 2992 |
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The Achromatic Telescopic Squeezing (ATS) [1] scheme offers new techniques to deliver unprecedentedly small beam spot size at the interaction points of the ATLAS and CMS experiments of the LHC, while perfectly controlling the chromatic properties of the corresponding optics (linear and non-linear chromaticities, off-momentum beta-beating, spurious dispersion induced by the crossing bumps). The first series of beam tests with ATS optics were achieved during the LHC Run I (2011/2012) for a first validation of the basics of the scheme at small intensity. In 2016, a new generation of more performing ATS optics was developed and more extensively tested in the machine, still with probe beams for optics measurement and correction at β*=10 cm, but also with a few nominal bunches to establish first collisions at nominal β* (40 cm) and beyond (33 cm), and to analysis the robustness of these optics in terms of collimation and machine protection. The paper will highlight the most relevant and conclusive results which were obtained during this second series of ATS tests.
[1] S. Fartoukh , Phys. Rev. ST Accel. Beams 16, 111002 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK030 | |
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| THPAB042 | Long-Range Beam-Beam Orbit Effects in LHC, Simulations and Observations From Machine Operation in 2016 | 3799 |
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| To limit the number of head on collisions to only one at the interaction point in the Large Hadron Collider (LHC), two beams are colliding with a non zero crossing angle. Under the presence of such angle the closed orbits of the individual bunches in the bunch train varies due to the long-range beam-beam effects. These variations leave a signature as a non zero transverse offset at the collision points visible in the front and trail of the bunch train. When operation team aims for the optimised beam orbit and therefore maximised luminosity, those front and tail bunches due to the overall offset experience reduced luminosity. This paper describes an overview of the existing tool for simulating these effects and compares to operational data. The effects of different operational scenarios (i.e. beam brightness, reduced or asymmetric crossing angles between the interaction points etc.) are simulated and discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB042 | |
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