| Paper | Title | Page |
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| MOPMR029 | Experience with DOROS BPMs for Coupling Measurement and Correction | 303 |
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| The Diode ORbit and OScillation System (DOROS) system is designed to provide accurate measurements of the beam position in the LHC. The oscillation part of the system, which is able to provide turn-by-turn data, is used to measure the transverse coupling. Since the system provides high resolution measurements for many turns only small excitations are needed to accurately measure the transverse coupling. In this article we present the performance the system to measure coupling and compare it to the BPMs not equipped with this system. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR029 | |
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| TUPMW030 | Review of LHC On-line Model Implementation and of its Applications | 1505 |
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| The online model of the LHC aims to provide an accurate description of the machine at any given time. In order to do so it extracts the current optics in the machine along with other crucial parameters. It also provides the functionality to match the measured orbit using virtual correctors and the measured beta functions using virtual quadrupoles. In this way an accurate effective model can be created. In order to facilitate the use of the online model a graphical user interface has been developed. In this article we describe the design of the online model and its application in different studies. We give examples how it has been used to predict the influence of changes before they were applied to the machine. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW030 | |
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| WEPOR006 | Demonstration of CLIC Level Phase Stability using a High Bandwidth, Low Latency Drive Beam Phase Feedforward System at the CLIC Test Facility CTF3 | 2673 |
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Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu-CARD, grant agreement no.~227579. The CLIC acceleration scheme, in which the RF power used to accelerate the main high energy beam is extracted from a second high intensity but low energy beam, places strict requirements on the phase stability of the power producing drive beam. To limit luminosity loss caused by energy jitter leading to emittance growth in the final focus to below 1%, 0.2 degrees of 12 GHz, or 50 fs, drive beam phase stability is needed. A low-latency phase feedforward correction with bandwidth above 17.5 MHz will be used to reduce the drive beam phase jitter to this level. The proposed scheme corrects the phase using fast electromagnetic kickers to vary the path length in a chicane prior to the drive beam power extraction. A prototype of this system has been installed at the CLIC test facility CTF3 to prove its feasibility. The latest results from the system are presented, demonstrating phase stabilisation in agreement with simulations given the beam conditions and power of the kicker amplifiers. Necessary improvements in the phase monitor performance and optics corrections made to remove the phase-energy dependence via R56 in order to achieve this level of stability are also discussed. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR006 | |
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| WEPOR007 | Recent Improvements in Drive Beam Stability in CTF3 | 2677 |
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| The proposed Compact Linear Collider (CLIC) uses a high intensity, low energy drive beam producing the RF power to accelerate the low intensity main beam with 100 MeV/m gradient. This scheme puts stringent requirements on drive beam stability in terms of phase, energy and current. Finding and understanding the sources of jitter plays a key role in their mitigation. In this paper, we report on the recent studies in the CLIC Test Facility (CTF3). New jitter and drift sources were identified and adequate beam-based feed-backs were implemented and commissioned. Finally, we present the resulting improvement of drive beam stability. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR007 | |
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| THPMB041 | Optics-measurement-based BPM Calibration | 3328 |
| SUPSS047 | use link to see paper's listing under its alternate paper code | |
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| The LHC beta functions (β) can be measured using the phase or the amplitude of betatron oscillations obtained with beam position monitors (BPMs). Using the amplitude information results in a β measurement affected by BPM calibration. This work aims at calibrating BPMs using optics measurements. For this, βs from amplitude and phase and normalized dispersion obtained from many different measurements in 2015 with different optics and corrections are analyzed. Simulations are also performed to support the analyses. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB041 | |
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| THPMB044 | Limitations on Optics Measurements in the LHC | 3339 |
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| In preparation of the optics commissioning at an energy of 6.5 TeV, many improvements have been done to cope with the expected reduced signal to noise ratio due to lowered bunch intensities imposed by machine protection considerations. This included, among others, an increase of the flat top duration of the AC dipole excitations, which allowed to use more turn-by-turn data for the analysis. The longer data acquisition revealed slow drifts of the optics, which limited the increased measurement precision. Furthermore, we will present how orbit drifts influenced dispersion measurements and, as a consequence, posed another limitation for the optics correction. In this paper we will discuss the implications of these observations for the measurement and correction of the optics. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB044 | |
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| THPMB045 | Comparison of Optics Measurement Methods in ESRF | 3343 |
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| The N-BPM and the Amplitude methods, which are used in the LHC for beam optics measurement, were applied to the ESRF storage ring. We compare the results to the Orbit Response Matrix (ORM) method that is routinely used in the ESRF. These techniques are conceptually different since the ORM is based on the orbit response upon strength variation of steering magnets while the LHC techniques rely on the harmonic analysis of turn-by-turn position excited by a kicker or an AC dipole. Finally, we compare these methods and show the differences in their performance in the ESRF environment. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB045 | |
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| THPMB046 | Status and Plans for Completion of the Experimental Programme of the Clic Test Facility Ctf3 | 3347 |
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| The CLIC Test Facility CTF3 was build, commissioned and operated at CERN by an international collaboration, with the aim of validating the CLIC two beam acceleration scheme, in which the RF power used to accelerate e+/e− beams is extracted from a high intensity electron beam. In the past years the main issues of such a scheme were assessed, demonstrating its feasibility. The CTF3 experimental programme is complementing these results by addressing cost and performance subjects, mainly using the CALIFES test beam injector and a full scale two-beam module. In this paper we document the present status and give an outlook to next year run, when the experimental programme should be completed. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB046 | |
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| THPMR038 | Non-Linear Errors in the Experimental Insertions of the LHC | 3472 |
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| Correction of nonlinear magnetic errors in low-β insertions can be of critical significance for the operation of a collider. This is expected to be of particular relevance to LHC Run II and the HL-LHC upgrade, as well as to future colliders such as the FCC. Current correction strategies for these accelerators have assumed it will be possible to calculate optimized local corrections through the insertions using a magnetic model of the errors. To test this assumption the nonlinear errors in the LHC experimental insertions have been examined via feed-down and amplitude detuning. It will be shown that while in some cases the magnetic measurements provide a sufficient description of the errors, in others large discrepancies exist which will require beam-based correction techniques. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR038 | |
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| THPMR039 | Commissioning of Non-linear Optics in the LHC at Injection Energy | 3476 |
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| Commissioning of the nonlinear optics at injection in the LHC was carried out for the first time in 2015 via beam-based methods. Building upon studies performed during Run I, corrections to the nonlinear chromaticity and detuning with amplitude were obtained. These corrections were observed to reduce beam-loss during measurement of linear optics. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR039 | |
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| THPMR040 | Local Optics Corrections in the HL-LHC IR | 3480 |
| SUPSS046 | use link to see paper's listing under its alternate paper code | |
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| For the high luminosity upgrade of the LHC optics correction in the interaction regions is expected to be challenged by the very low β* and the sizable expected quadrupolar errors in the triplet. This paper addresses the performance and limitations of the segment-by-segment technique to correct quadrupolar and skew quadrupolar errors in the HL-LHC IR via computer simulations. Required improvements to this technique and possible combinations with other correction approaches are also presented including experimental tests in the current LHC IR. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR040 | |
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| THPOR032 | Effect and Optimisation of Non-Linear Chromatic Aberrations of the CLIC Drive Beam Recombination at CTF3 | 3852 |
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| The CLIC design relies on the two-beam acceleration principle, i.e. the energy transfer from the so called drive beam to the main colliding beams. At the CLIC Test Facility (CTF3) at CERN the feasibility of this principle is being tested in terms of performance and achievable specifications. The high-current drive beam is generated by recombining its parts in a delay loop and a combiner ring. Preserving the drive beam emittance during the recombination process is crucial to ensure beam-current and power production stability. Present theoretical and experimental studies show that non-linear energy dependence of the transverse optics heavily spoils the quality of the recombined beam. Conventionally these effects are cured by means of non-linear corrections using sextupoles. In this work we propose a mitigation of these effects by optimising the linear lattice, leading to a more robust and easy to operate drive beam recombination complex. The latest results are presented. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR032 | |
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