| 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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| WEPMW028 | First Attempts at using Active Halo Control at the LHC | 2486 |
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Funding: Research supported by the High Luminosity LHC project. The beam halo population is a non-negligible factor for the performance of the LHC collimation system and the machine protection. In particular this could become crucial for aiming at stored beam energies of 700 MJ in the High Luminosity (HL-LHC) project, in order to avoid beam dumps caused by orbit jitter and to ensure safety during a crab cavity failure. Therefore several techniques to safely deplete the halo, i.e. active halo control, are under development. In a first attempt a novel way for safe halo depletion was tested with particle narrow-band excitation employing the LHC Transverse Damper (ADT). At an energy of 450 GeV a bunch selective beam tail scraping without affecting the core distribution was attempted. This paper presents the first measurement results, as well as a simple simulation to model the underlying dynamics. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW028 | |
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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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| 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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| THPMR044 | Short Term Dynamic Aperture with AC Dipoles | 3496 |
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| The dynamic aperture of an accelerator is determined by its non-linear components and errors. Control of the dynamic aperture is important for a good understanding and operation of the accelerator. The AC dipole, installed in the LHC for the diagnostic of linear and non-linear optics, could serve as a tool for the determination of the dynamic aperture. However, since the AC dipole itself modifies the non-linear dynamics, the dynamic aperture with and without AC dipole are expected to differ. This paper will report the results of studies of the effect of the AC dipole on the dynamic aperture. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR044 | |
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