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| MOPWO010 | Machine Protection Studies for a Crab Cavity in the LHC | 906 |
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Funding: US-LARP and CONACYT Crab cavities (CCs) apply a transverse kick that rotate the bunches so as to have a head-on collision at the interaction point (IP). Such cavities were successfully used to improve the luminosity of KEKB. They are also a key ingredient of the HL-LHC project to increase the luminosity of the LHC. As CCs can rapidly change the particle trajectories, machine protection studies are required to assess the beam losses due to fast CC failures. In this paper, we discuss the effect of rapid voltage or phase changes in a CC for the HL-LHC layout using measured beam distributions from the present LHC. |
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| MOPWO036 | Civil Engineering Feasibility Studies for Future Ring Colliders at CERN | 969 |
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| CERN civil engineers are studying the feasibility of future ring colliders to complement the LHC. Infrastructure works typically represent one third of the cost of major physics projects, so it's critical that the construction costs are well understood from the conceptual stage. This poster presents the first results of the feasibility studies for two potential ring colliders at CERN: the racetrack shaped Linac-Ring LHeC and an 80km circular tunnel to house the High Energy LHC (SHE-LHC) and the TLEP. Some of the key civil engineering challenges faced in such large scale projects are presented with particular emphasis on geology, design and risk. | ||
| MOPWO054 | The LHeC as a Higgs Boson Factory | 1017 |
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| The LHeC is designed to collide a new 60 GeV energy electron beam, from a 3-pass ERL, with the 7 TeV energy LHC proton beam. At the present target ep luminosity of 1033cm-2s-1, the LHeC would produce a few 1000 Higgs bosons per year, allowing for precision coupling measurements, especially of the H –> b bbar decay in charged current deep inelastic scattering (ep –> nu H X). With a significant increase of the luminosity, rarer channels become accessible, as the charm decay. Here such an increase, to the level of 1034cm-2s-1 or even beyond, is considered from a combination of improvements, namely with a smaller proton beam emittance, with a further reduction of the proton IP beta function, an increase of the proton bunch intensity and with doubling the lepton beam current, compared to the canonical values assumed in the CDR. | ||
| TUPFI002 | Electron Cloud and Scrubbing Studies for the LHC | 1331 |
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| Electron cloud build-up resulting from beam-induced multipacting is one of the major limitations for the operation of the LHC with beams with close bunch spacing. Electron clouds induce unwanted pressure rise, heat loads on the beam screens of the superconducting magnets and beam instabilities. Operation with bunch spacing of 50 ns in 2011 and 2012 has required decreasing the Secondary Electron Yield of the beam screens below the multipacting threshold for beams with this bunch spacing. This was achieved by continuous electron bombardment induced by operating the machine with high intensity beams with 50 and 25 ns spacing during dedicated periods at injection energy (450 GeV) and at top energy (3.5 and 4 TeV). The evolution of the Secondary Electron Yield during these periods, at different sections of the machine, can be estimated by pressure, heat load and by bunch-by-bunch RF stable phase measurements. The experimental information on the scrubbing process will be discussed and a possible “scrubbing strategy” to allow the operation with 50ns and 25ns beams after the Long Shutdown in 2013-2014 will be presented. | ||
| TUPFI005 | Synchrotron-Radiation Photon Distribution for Highest Energy Circular Colliders | 1340 |
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Funding: Acknowledgements to CINVESTAV, CERN and EPLANET project. At high energies, beam-induced synchrotron radiation is an important source of heating, beam-related vacuum pressure increase, and primary photoelectrons, which can give rise to an electron cloud. The photon distribution along the beam pipe wall is a key input to codes such as ECLOUD and PyECLOUD, which model the electron cloud build-up. For future high-energy colliders, like TLEP or SHE-LHC, photon stops and antechambers are considered in order to facilitate cooling and vacuum pressure control. We use the Synrad3D code developed at Cornell to simulate the photon distribution for the LHC. |
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| TUPFI030 | LHC Machine Developments in 2011-12 | 1406 |
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| In 2011 and 2012 LHC machine development (MD) sessions were performed during dedicated slots of beam time. These MD studies were scheduled and planned well in advance. Study topics reflected the previously agreed priorities, such as further optimizing machine performance, exploring beam parameters beyond design targets, assessing machine limitations, testing new concepts and machine settings, preparing future LHC running in view of the 2013/14 LHC shutdown and the re-commissioning of the LHC at nominal beam energy in 2014/15. We describe the planning, preparation, execution, review, and documentation of these LHC beam studies and highlight some key results. | ||
| TUPFI042 | Beam Parameters and Luminosity Time Evolution for an 80-km VHE-LHC | 1442 |
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| The Very High Energy LHC (VHE-LHC) is a recently proposed proton-proton collider in a new 80-km tunnel. With a dipole field of 15-20 T it would provide a collision energy of 76-100 TeV c.m. We discuss the VHE-LHC beam parameters and compute the time evolution of luminosity, beam current, emittances, bunch length, and beam-beam tune shift during a physics store. The results for VHE-LHC are compared with those for HE-LHC, a 33-TeV (20-T field) collider located in the existing LHC tunnel. | ||
| TUPFI043 | Matching Antisymmetric Arc Optics to Symmetric Interaction Region | 1445 |
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Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu- CARD, grant agreement no. 227579. Considering a generic double-ring collider, we discuss the matching from an antisymmetric optics in the arcs to a symmetric optics in the interaction region (IR) by means of an antisymmetric matching section (MS). As an example, we present an application to the LHC, for which a symmetric IR with extremely flat beams is under study. |
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| TUPFI044 | LHC Optics with Crab-waist Collisions and Local Chromatic Correction | 1448 |
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Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu- CARD, grant agreement no. 227579. We report the status of the optics design for a local chromatic correction with extremely-flat beams at the LHC. Together with a Large Piwinski angle, this optics opens up the possibility of crab-waist collisions at the LHC, for which a new layout of the LHC insertion region (IR) is needed. We present a complete optics and discuss the parameters of the final "double-half" quadrupole. |
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| TUPFI045 | Electron-cloud Maps for LHC Scrubbing Optimization | 1451 |
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| Electron-cloud maps as alternative to detailed build-up simulations have already been applied in the past for a few accelerators, e.g. RHIC and the LHC at 7 TeV. We here report a first application of maps to optimize the "beam scrubbing" of the LHC arcs at injection energy: Maps are used to efficiently determine the optimum bunch filling pattern which maximizes the electron flux on the chamber wall, while respecting constraints on the central cloud density to ensure beam stability. In addition, new features have been explored, e.g. by introducing thresholds which divide regions where either linear maps or cubic maps best describe the build-up and the decay of an electron cloud. In the near future we plan to extend the map formalism to individual slices in a dipole file in order to represent the vertical "stripes". | ||
| TUPME011 | Simulated Beam-beam Limit for Circular Higgs Factories | 1586 |
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| We report simulation studies of the beam-beam limit for two proposed circular e+e− Higgs factories with circumference of 27 and 80 km, respectively, called LEP3 and TLEP. In particular we investigate the dependence of the steady-state luminosity and transverse beam sizes on the synchrotron tune (or momentum compaction factor) and on the betatron tunes, as well as the consequences of the strong radiation damping and the implications of the large hourglass effect. | ||
| TUPME040 | TLEP: High-performance Circular e+e− Collider to Study the Higgs Boson | 1658 |
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| The recent discovery of a light Higgs boson has opened up considerable interest in circular e+e− Higgs factories around the world. We report on the progress of the “TLEP3” concept since last year. Two options are considered: LEP3, a 240 GeV centre-of-mass (Ecm) e+e− machine in the LHC tunnel with cost only a fraction of the cost of an equivalent linear collider, due to the use of existing infrastructure and the two general-purpose LHC detectors, and TLEP, an e+e− machine in a new 80 km tunnel that can operate up to an Ecm of 350 GeV. Both concepts enjoy the extensive know-how on circular colliders and how to deliver their design luminosity, and the existence of up to four interaction points. The attainable luminosities are 1034/cm2/s and 5x1034/cm2/s per interaction point for LEP3 and TLEP respectively. Both machines can operate as Tera-Z and Mega-W boson factories, giving decisive opportunities for over-constraining the electroweak sector of the Standard Model. The technical challenges and possible ways to improve the performance further will be discussed. | ||
| TUPME055 | Strawman Optics Design for the CERN LHeC ERL Test Facility | 1694 |
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| In preparation for a future Large Hadron electron Collider (LHeC) at CERN, an ERL test facility is foreseen as a test bed for SRF development, cryogenics, and advanced beam instrumentation, as well as for studies of ERL-specific beam dynamics. The CERN ERL test facility would comprise two linacs, each consisting of 4 superconducting 5-cell cavities at 802 MHz, and two return arcs on either side. With an RF voltage of 75 MeV per linac a final electron energy of about 300 MeV is reached. The average beam current should be above 6 mA to explore the parameter range of the future LHeC. In this paper we present a preliminary optics layout. | ||
| TUPME056 | 3.5 GeV Superconducting Stacking Ring for Compton Based Polarized Positrons Source of CLIC | 1697 |
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| This paper describes 3.5 GeV superconducting storage ring dedicated to positron accumulation as part of a polarized positron source for CLIC, based on Compton scattering in a Compton storage ring. The superconducting stacking ring can provide a synchrotron damping time of order 250 microseconds. Together with combined injection scheme in the longitudinal and transverse plane, such a ring may solve the problem of accumulating a positron beam with efficiency close to 95 % and with the beam intensity required for CLIC. | ||
| TUPWA050 | Effect of Transverse Coupling on Asymmetric Cooling in Compton Rings | 1823 |
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| Fast cooling of bunches circulating in a Compton ring is achieved by placing the collision point between electron bunches and laser pulses in a dispersive section and by, in addition, introducing a transverse offset between the laser pulse and the electron-beam closed orbit. Growth of the emittance in the dispersive transversal direction due to the additional excitation of betatron oscillations limits this type of cooling. Here we present the results of further studies on the fast cooling process, looking at the effect of the coupling of the transverse (betatron) oscillations. We first show theoretically that the transverse betatron coupling shortens the cooling time and hence reduces the steady-state energy spread of the electron beam, as well as the quantum losses. The theoretical estimates are then validated by simulations. Finally, a proof-of-principle experiment at the KEK ATF Damping Ring is proposed. | ||