| Paper | Title | Page |
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| TUPRO003 | Fast Crab Cavity Failures in HL-LHC | 997 |
| SUSPSNE004 | use link to see paper's listing under its alternate paper code | |
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| Crab cavities (CCs) are a key ingredient of the High-Luminosity Large Hadron Collider (HL-LHC) to ensure head on collisions at the main experiments (ATLAS and CMS) and fully profit from the smaller β* provided by the ATS optics. At KEKB, CCs have exhibited abrupt changes of phase and voltage during a time period of few LHC turns and considering the large energy stored in the HL-LHC beam, CC failures represent a serious risk to the LHC machine protection. In this paper, we discuss the effect of CC voltage or phase changes on a time interval similar to, or longer than, necessary to dump the beam. The simulations assume a realistic steady-state distribution to assess the beam losses for the HL-LHC. Additionally, some strategies are studied to mitigate the damage caused by the failures. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO003 | |
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| TUPRO010 | Origins of Transverse Emittance Blow-up during the LHC Energy Ramp | 1021 |
| SUSPSNE003 | use link to see paper's listing under its alternate paper code | |
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| During LHC Run 1 about 30 % of the potential peak performance was lost due to transverse emittance blow-up through the LHC cycle. Measurements indicated that the majority of the blow-up occurred during the energy ramp. Until the end of LHC Run 1 this emittance blow-up could not be eliminated. In this paper the measurements and observations of emittance growth through the ramp are summarized. Simulation results for growth due to Intra Beam Scattering will be shown and compared to measurements. A summary of investigations of other possible sources will be given and backed up with simulations where possible. Requirements for commissioning the LHC with beam in 2015 after Long Shutdown 1 to understand and control emittance blow-up will be listed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO010 | |
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| TUPRO011 | New Tools for K-modulation in the LHC | 1024 |
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| For many applications, the precise knowledge of the beta function at a given location is essential. Several measurement techniques for optics functions are used in the LHC to provide the most suitable method for a given scenario. A new tool to run k-modulation measurements and analysis is being developed with the aim to be fully automatic and online. It will take constraints of various systems such as tune measurement precision, powering limits of the LHC superconducting circuits and limits of their quench protection systems into account. It will also provide the possibility to sinusoidally modulate the currents of the investigated quadrupoles with a predefined frequency and amplitude to increase the measurement precision further. This paper will review the advantages and limitations of k-modulation measurements in the LHC with and without sinusoidal current modulation. The used algorithms and tools will be presented and estimates on the obtainable beta function measurement precision will be given. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO011 | |
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| TUPRO017 | HL-LHC Performance with a 200 MHz RF System | 1043 |
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| The HL-LHC performance could considerably benefit from having a 200 MHz RF system. This would allow to inject longer bunches with larger bunch intensity from the SPS and to perform bunch length leveling if required. We also consider the possibility of decreasing the crab cavity frequency to increase both virtual peak luminosity and luminous region. Performance estimates of various configurations are presented in this paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO017 | |
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| TUPRO018 | Prospects for the LHC Optics Measurements and Corrections at Higher Energy | 1046 |
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| LHC will resume operation in 2015 at 6.5 TeV. The higher energy allows for smaller IP beta functions, further enhancing the optics errors in the triplet quadrupoles. Moreover the uncertainty in the calibration of some quadrupoles will slightly increase due to saturation effects. The complete magnetic cycle of the LHC will take longer due to the higher energy and extended squeeze sequence. All these issues require more precise and more efficient optics measurements and corrections to guarantee the same optics quality level as in 2012 when a 7% peak beta-beating was achieved. This paper summarizes the on-going efforts for achieving faster and more accurate optics measurements and corrections. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO018 | |
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| TUPRO019 | Localisation of Beam Offset Jitter Sources at ATF2 | 1049 |
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| For the commissioning and operation of modern particle accelerators, automated error detection and diagnostics methods are becoming increasingly important. In this paper, we present two such methods, which are capable of localising sources of beam offset jitter with a combination of correlation studies and so called degree of freedom plots. The methods were applied to the ATF2 beam line at KEK, where one of the major goals is the reduction of the beam offset jitter. Results of this localisation are shown in this paper. A big advantage of the presented method is its high robustness especially to varying optics parameters. Therefore, we believe that the developed beam offset jitter localisation methods can be easily applied to other accelerators. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO019 | |
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| TUPRO062 | Improvements in the Optics Measurement Resolution for the LHC | 1177 |
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| Optics measurement algorithms which are based on the measurement of beam position monitor (BPM) turn-by-turn data are currently being improved in preparation for the commissioning of the LHC at higher energy. The turn-by-turn data of one BPM may be used more than once, but the implied correlations were not considered in the final error bar. In this paper the error propagation including correlations is studied for the statistical part of the uncertainty. The confidence level of the measurement is investigated analytically and with simulations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO062 | |
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| TUPRO069 | First Studies of Two-beam Tuning in the CLIC BDS | 1195 |
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| Beam tuning in the beam delivery system (BDS) is one of the major challenges for the future linear colliders. Up to now single beam tuning has been performed, both in simulations and experiments at the Accelerator Test Facility (ATF). However, in future linear colliders, due to fast detuning of the final focus optics both beamlines will need to be tuned simultaneously. In this paper a first two-beam tuning study for the Compact Linear Collider (CLIC) BDS is presented applying the usual toolbox of beam-based alignment (BBA) and sextupole knobs. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO069 | |
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| TUPRO070 | LHeC IR Optics Design Integrated into the HL-LHC Lattice | 1198 |
| SUSPSNE049 | use link to see paper's listing under its alternate paper code | |
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Funding: OPAC fellowship funded by European Union under contract PITN-GA-2011-289485 The LHeC is a proposed upgrade to the LHC to provide electron-proton collisions and explore the new regime of energy and intensity for lepton-nucleon scattering. The work presented here investigates optics and layout solutions allowing simultaneous nucleon-nucleon and lepton-nucleon collisions at separate interaction points compatible with the proposed HL-LHC lattice. A first lattice design has been proposed that collides proton beam 2 with the electron beam. The nominal design calls for a β* (beta function in the interaction point ) of 10 cm using an extended version of the Achromatic Telescopic Squeezing (ATS) scheme, and a L* (distance to the inner triplet) of 10 m. Modifying these two parameters, β* and L*, can provide benefits to the current design since the values of these parameters have direct effects on the luminosity, the natural chromaticity and the synchrotron radiation of the electron beam. This work aims to explore the range over which these parameters can be varied in order to achieve the desired goal. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO070 | |
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| TUPME004 | Lowering the CLIC IP Horizontal Beta Function | 1340 |
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| In order to alleviate the beamstrahlung photon emission, the beams at the CLIC Interaction Point must be flat. We propose to explore this limit reducing the horizontal beta function for CLIC at 500 GeV c.o.m. energy to half of its nominal value. This could increase the photon emission but it also increases luminosity and might allow reducing the bunch charge keeping the same luminosity. This configuration can also be considered for lower energies where beamstrahlung is less critical. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME004 | |
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| TUPME005 | CLIC FFS Lattice Proposals Combining Local and Non-local Chromaticity Corrections | 1343 |
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| The requirements on the Final Focusing System (FFS) for a new linear collider has lead to lattice designs where chromaticity is corrected either locally or non-locally. Here, alternative proposals of lattice design are presented for the current CLIC 500GeV beam parameters, combining the local chromaticity correction on the vertical plane and non-local correction on the horizontal. The tight tolerance on phase advances and beta functions imposed to obtain -I transformation required to cancel the chromatic terms is relaxed by enlarging the system length and using a more general transformation definition, aiming to obtain better results in tuning simulations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME005 | |
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| TUPME006 | Considerations for a QD0 with Hybrid Technology in ILC | 1346 |
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| The baseline design of the QD0 magnet for ILC, the International Linear Collider, is a very compact superconducting quadrupole (coil-dominated magnet). A prototype of this quadrupole is under construction at Brookhaven National Laboratory (USA). In CLIC, the Compact Linear Collider under study at CERN, we are studying another conceptual solution for the QD0. This is due to two main reasons: all the magnets of the Beam Delivery System will need to be stabilized in the nano-meter range and extremely tight alignment tolerances are required. The proposed solution, now baseline for CLIC, is a room temperature hybrid quadrupole based on electromagnetic coils and permanent magnet blocks (iron-dominated magnet). In this paper we present a conceptual design for a hybrid solution studied and adapted also to the ILC project. A special super-ferric solution is proposed to make the cross section compatible with the experiments layout. This design matches the compactness requirement with the advantages of stability and alignment precision, aspects critical also for ILC in order to achieve the design luminosity. Final Focus optics design considerations for this solution are also presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME006 | |
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| TUPME008 | Status of the CLIC-UK R&D Programme on Design of Key Systems for the Compact Linear Collider | 1354 |
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| Six UK institutes are engaged in a collaborative R&D programme with CERN aimed at demonstrating key aspects of technology feasibility for the Compact Linear Collider (CLIC). We give an overview and status of the R&D being done on: 1) Drive-beam components: quadrupole magnets and the beam phase feed-forward prototype. 2) Beam instrumentation: stripline and cavity beam position monitors, an electro-optical longitudinal bunch profile monitor, and laserwire and diffraction and transition radiation monitors for transverse beam-size determination. 3) Beam delivery system and machine-detector interface design, including beam feedback/control systems and crab cavity design and control. 4) RF structure design. In each case, where applicable, we report on the status of prototype systems and performance tests with beam at the CTF3, ATF2 and CesrTA test facilities, including plans for future experiments. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME008 | |
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| TUPRI014 | Modelling and Long Term Dynamics of Crab Cavities in the LHC | 1578 |
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Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan. The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) aims to achieve an integrated luminosity of 250-300 fb-1 per year. This upgrade includes the use crab cavities to mitigate the geometric loss of luminosity arising from the beam crossing angle. The tight space constraints at the location of the cavities leads to cavity designs which are axially non-symmetric and have a potentially significant effect on the long term dynamics and dynamic aperture of the LHC. In this paper we present the current status of advanced modelling of crab cavities. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI014 | |
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| THPRO080 | The FiDeL Model at 7 TeV | 3069 |
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| After the long shut down of 2013-2014, the LHC energy will be pushed toward 7 TeV. In this range of energy, the main magnets will enter a new regime. For this reason, this paper will present a detailed study of the performance of the FiDeL model that could be critical for the operation in 2015. In particular this paper will study the saturation component and its precision in the model, together with the hysteresis error. The effect of these two components and their errors on the beta-beating is also given. Furthermore, an estimate of the dynamic effects visible in the tune and chromaticity will be presented for the 7 TeV operation. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO080 | |
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| THPRO081 | Simulation and Observation of Driven Beam Oscillations with Space Charge in the CERN PS Booster | 3073 |
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Funding: This project has been supported by a Marie Curie Early Initial Training Network Fellowship of the European Community's Seventh Framework Programme, contract number (PITN-GA-2011-289485-OPAC). As part of the LHC Injector Upgrade project, the CERN PS Booster will operate at higher injection and extraction energies and with nearly a factor of two increase in beam brightness. In order to better understand the machine’s limitations, a campaign of nonlinear optics measurements from turn-by-turn trajectory measurements is planned for after Long Shutdown 1. The goal of this work is to establish an efficient procedure for implementing a resonance compensation scheme after the machine’s injection energy is increased. The trajectory measurement system is expected initially to require high intensity beam in order to have good position measurement resolution, so understanding space charge effects will be important for optics analysis. We present the results of simulations of driven beam oscillations with space charge effects, and comparison with trial beam trajectory measurements. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO081 | |
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| THPRO082 | Observation of Coherent Instability in the CERN PS Booster | 3076 |
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Funding: This project has been supported by a Marie Curie Early Initial Training Network Fellowship of the European Community's Seventh Framework Programme, contract number (PITN-GA-2011-289485-OPAC). At high intensities and at a certain working point an instability develops in the CERN PS Booster, and large coherent transverse oscillations and beam loss occur. The coherent oscillations and beam loss can be effectively controlled with the transverse damper system, but the origin of the instability is not well-understood. Recent measurements with the PSB's new trajectory measurement system have provided some insight into the nature of this instability, and these observations are presented here. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO082 | |
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| THPRI010 | FCC-ee Final Focus with Chromaticity Correction | 3782 |
| SUSPSNE005 | use link to see paper's listing under its alternate paper code | |
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| A 100 km circular electron-positron collider is considered as one of the possible future high energy facilities. In order to achieve a high luminosity, strong beam focusing at the Interaction Point is used requiring the correction of the chromatic aberrations. In this paper we study preliminary designs of a Final Focus System for the TLEP collider with chromatic correction. Beam orbit stability and dynamic aperture calculations are also presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI010 | |
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| THPRI012 | Tuning of the Compact Linear Collider Beam Delivery System | 3788 |
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| Tuning the CLIC Beam Delivery System (BDS), and in particular the final focus, is a challenging task. In simulations without misalignments, the goal is to reach 120~\% of the nominal luminosity target, in order to allow for 10~\% loss due to static imperfections, and another 10~\% loss from dynamic imperfections. Various approaches have been considered to correct the magnet misalignments, including 1-1 correction, dispersion free steering (DFS), and several minimization methods utilizing multipole movers. In this paper we report on the recent advancements towards a feasible tuning approach that reach the required luminosity target in a reasonable time frame. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI012 | |
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