| Paper | Title | Page |
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| TUPFI011 | Study and Operational Implementation of a Tilted Crossing Angle in LHCb | 1349 |
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| The current crossing angle scheme at LHCb interaction point (horizontal crossing angle and vertical beam separation) prohibits the use of the LHCb dipole positive polarity for 25 ns bunch spacing operation since the beam separation at the first parasitic encounter is very small inducing unwanted beam encounters. To overcome this limitation a different crossing angle scheme was proposed in 2007 by W. Herr and Y. Papaphilippou. The new schema implies a vertical external crossing angle that together with the horizontal internal crossing angle, from the LHCb dipole and its three compensator magnets, defines a new tilted crossing and separation plane providing enough beam separation at the parasitic encounters. This paper summarizes the feasibility study of the new crossing scheme, the implementation in routine operation and analyzes the beam stability during the building up of the tilted crossing plane. | ||
| TUPFI023 | Optics Design and Lattice Optimisation for the HL-LHC | 1385 |
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Funding: The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Cap. Spec. Progr, Grant Agreement 284404. The luminosity upgrade project of the LHC collider at CERN is based on a strong focusing scheme to reach smallest beam sizes at the collision points. Depending on the available magnet technology (Nb3Sn or NbTi) a number of beam optics has been developed to define the specifications for the new super conducting quadrupoles. In the context of the optics matching new issues have been addressed and new concepts have been used: Quadrupole strength flexibility and chromatic corrections have been studied, as well as the influence of quadrupole fringe fields. The lattice has been optimised including the needs of the foreseen crab cavities and the transition between injection and low β optics had to guarantee smooth gradient changes over a wide range of β* values. Tolerances on misalignments and power converter ripple have been re-evaluated. Finally the combination of the quadrupole strengths in the high luminosity matching sections with those in the neighboring sectors is explained, a key concept of the ATS to reach smallest β* values. This paper presents the results obtained within the HiLumi collaboration Task 2.2 and summarises the main parameters of the project. |
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| WEPEA058 | LSS Layout Optimizations for Low-beta Optics for the HL-LHC | 2639 |
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Funding: The HiLumi LHC Design Study is included in the HL-LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404 The High Luminosity LHC (HL-LHC) project aims to upgrade the existing LHC to a peak luminosity of the order 1035cm-2s−1, while retaining as much of the nominal layout and hardware as possible. The current baseline for this upgrade is the use of the Achromatic Telescopic Squeeze (ATS) concept, which allows mini-Beta squeeze in IRs 1 and 5 (ATLAS and CMS respectively) far below that possible with nominal optics. However it is useful to both explore the parameter space of the ATS scheme while also attempting to push the boundaries of the nominal layout. This paper presents a study into maximising optical flexibility of the nominal LHC Long Straight Sections (LSSs) around IPs 1 and 5. This involves replacing, moving or adding magnets within the LSS to investigate feasibility of exploiting a more conventional optical scheme than the ATS scheme. In particular the option of replacing single LSS quadrupoles with doublets is explored. The study also looks at making similar changes to the LSS while also implementing the ATS scheme, to further explore the ATS parameter space with the benefit of experience gained into flexibility of a modified nominal LHC optical scheme. |
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| WEPEA059 | Study of the Impact of Fringe Fields of the Large Aperture Triplets on the Linear Optics of the HL-LHC | 2642 |
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Funding: The HiLumi LHC Design Study is included in the HL-LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404 High-luminosity hadron colliders such as the High Luminosity LHC (HL-LHC) project place demanding requirements on existing and new magnet technology. The very low β* achieved by the Achromatic Telescopic Squeeze (ATS) optics scheme* for the HL-LHC in particular, requires large apertures in the high gradient Nb3Sn final focusing inner triplet triplet. Such magnets have extended fringe fields which perturb the linear and non-linear optics. This paper presents results of studies into the liner optics of the LHC using a range of fringe field models, including measurements of fringe fields from prototype magnets, and presents calculations of the beta-beating in the machine. Furthermore a similar study is presented on the nominal LHC optics, which uses final focus quadrupoles of higher gradient but significantly smaller aperture. * S. Fartoukh, ‘’An Achromatic Telescopic Squeezing (ATS) Scheme for LHC Upgrade’’, in proceedings of IPAC11, p. 2088. |
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