Keyword: beam-losses
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MOPMF042 Crab Cavity Failures Combined with a Loss of the Beam-Beam Kick in the High Luminosity LHC cavity, luminosity, dumping, collimation 192
 
  • B. Lindstrom, H. Burkhardt, V.K.B. Olsen, A. Santamaría García, K.N. Sjobak, M. Valette, D. Wollmann
    CERN, Geneva, Switzerland
 
  Crab cavities are an essential component of the High Luminosity LHC (HL-LHC) project. In case of a failure they can create large transverse kicks on the beam within tens of microseconds and, therefore, require a fast extraction of the circulating beam. In this paper, the effects of different crab cavity failures in combination with the missing beam-beam kick following the dump of only one LHC beam are presented and consequences for the interlocking strategy of crab cavities are discussed.
Work supported by the High Luminosity LHC project.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF042  
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MOPMF063 Asynchronous Beam Dump Tests at LHC proton, extraction, quadrupole, operation 265
 
  • C. Wiesner, W. Bartmann, C. Bracco, E. Carlier, L. Ducimetière, M.I. Frankl, M.A. Fraser, B. Goddard, C. Heßler, T. Kramer, A. Lechner, N. Magnin, V. Senaj, D. Wollmann
    CERN, Geneva, Switzerland
 
  The detailed understanding of the beam-loss pattern in case of an asynchronous beam dump is essential for the safe operation of the future High Luminosity LHC (HL-LHC) with nearly twice the nominal LHC beam intensity, leading to correspondingly higher energy deposition on the protection elements. An asynchronous beam dump is provoked when the rise time of the extraction kickers is not synchronized to the 3 us long particle-free abort gap. Thus, particles that are not absorbed by dedicated protection elements can be lost on the machine aperture. Since asynchronous beam dumps are among the most critical failure cases of the LHC, experimental tests at low intensity are performed routinely. This paper reviews recent asynchronous beam dump tests performed in the LHC. It describes the test conditions, discusses the beam-loss behaviour and presents simulation and measurement results. In particular, it examines a test event from May 2016, which led to the quench of four superconducting magnets in the extraction region and which was studied by a dedicated beam experiment in December 2017.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF063  
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TUPAF029 Observation of Fast Losses in the LHC Operation in 2017 operation, detector, betatron, monitoring 740
 
  • A.A. Gorzawski, N. Fuster-Martínez, S. Redaelli, C. Xu, C. Zamantzas
    CERN, Geneva, Switzerland
  • R.B. Appleby
    UMAN, Manchester, United Kingdom
  • H. Garcia Morales
    Royal Holloway, University of London, Surrey, United Kingdom
 
  Four diamond detectors that provide beam loss measurements with time resolution in the nanosecond range were added in the vicinity of the primary collimators of the Large Hadron Collider (LHC). This is a powerful diagnostic tool that provides the unique chance to measure bunch-by-bunch losses. The operation of the LHC in 2017 presented several unusual events of fast, high intensity beam losses, many of them captured by the diamond detectors in the betatron cleaning region. In this paper we review some of the relevant loss cases that were analyzed in the wider scope of determining the source of the instability generating these losses. We show few of the possible applications of this detectors in daily operations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF029  
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TUPAF049 Analysis of Loss Signatures of Unidentified Falling Objects in the LHC proton, operation, vacuum, electron 814
 
  • L. K. Grob, M. Dziadosz, E.B. Holzer, A. Lechner, B. Lindstrom, R. Schmidt, D. Wollmann, C. Zamantzas
    CERN, Geneva, Switzerland
 
  Particulates in the LHC beam pipes can interact with the proton beams and cause significant beam losses. The "UFOs" (unidentified falling objects) hypothesis describes a particle falling into the beam, creating particle showers, being ionized and repelled. Though the signals of the beam loss monitors support this, many aspects remain unknown. Neither the source of the dust nor the release mechanism from the beam pipe are understood. The same holds for the forces involved in the interaction and the observed UFO rate reduction over the years. These open questions are approached from different angles. Firstly, a new data analysis tool was established featuring advanced raw data selection and statistical analysis. Results of this analysis will be presented. Secondly, dust samples were extracted from LHC components and analyzed to gain insight into the size distribution and material composition of the contamination. The performed observations and analysis lead to a better modelling of the UFO events and helped to understand the physics involved. The validated UFO models will be crucial in view of the high luminosity upgrade of the LHC (HL-LHC) and the Future Circular Collider (FCC).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF049  
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TUPAL034 Effect of 805-MHz Linac RF Stability on Beam Losses in LANSCE High-Energy Beamlines linac, neutron, proton, operation 1078
 
  • Y.K. Batygin
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
Operation of an accelerator facility critically depends on stability of the field amplitudes and phases of the accelerating cavities. The LANSCE linear accelerator consists of a 201.25-MHz, drift-tube linac and an 805-MHz, side-coupled-cavity linac (SCL). Beam losses in the high-energy beamlines of the 800-MeV facility were measured versus variation of the amplitudes and phases of the 805-MHz, SCL, RF cavities. A recent study* confirms that to achieve low losses, the stability of the amplitudes and phases should be kept within 0.1% and 0.1o, respectively. This agrees with a previous study of beam losses in the 201.25-MHz linac. Details of the measurements and results are presented.
*L.J.Rybarcyk, R.C.McCrady, Proceeding of LINAC2016, East Lansing, MI, USA, MOPLR072, p.301.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL034  
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WEPAF078 Machine Learning Applied at the LHC for Beam Loss Pattern Classification collimation, injection, proton, flattop 2020
 
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
  • B. Salvachua
    CERN, Geneva, Switzerland
 
  Beam losses at the LHC are constantly monitored because they can heavily impact the performance of the machine. One of the highest risks is to quench the LHC superconducting magnets in the presence of losses leading to a long machine downtime in order to recover cryogenic conditions. Smaller losses are more likely to occur and have an impact on the machine performance, reducing the luminosity production or reducing the lifetime of accelerator systems due to radiation effects, such as magnets. Understanding the characteristics of the beam loss, such as the beam and the plane, is crucial in order to correct them. Regularly during the year, dedicated loss map measurements are performed in order to validate the beam halo cleaning of the collimation system. These loss maps have the particular advantage that they are performed in well controlled conditions and can therefore be used by a machine learning algorithm to classify the type of losses during the LHC machine cycle. This study shows the result of the beam loss classification and its retrospective application to beam loss data from the 2017 run.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF078  
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WEPAL023 Pulsed Operation at MAMI with High Beam Loading experiment, operation, klystron, beam-loading 2206
 
  • M. Dehn, K. Aulenbacher, F. Fichtner, P. Jennewein, W. Klag, H.-J. Kreidel, J.R. Röthgen
    IKP, Mainz, Germany
 
  Funding: Work supported by DFG (CRC 1044) and the German federal state of Rhineland-Palatinate
The Mainz Microtron Accelerator (MAMI) is a microtron cascade which is normally operated CW for particle physics experiments. For certain investigations it is necessary to use a pulsed beam (macro pulses, several milliseconds). Up to now this pulsed mode can only be applied if the beam loading for the accelerating RF structures is negligible. To achieve higher pulse intensities the accelerator RF infrastructure needs to be equipped with feed-forward techniques to compensate for the expected beam loading. To monitor beam losses the machine protection system at MAMI needs to be extended to be able to localize fast occurrences of beam losses. This paper will present the possibilities being investigated to allow pulsed operation of MAMI within the near future.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL023  
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THYGBD2 Results of UFO Dynamics Studies with Beam in the LHC experiment, emittance, proton, simulation 2914
 
  • B. Lindstrom, A. Apollonio, P. Bélanger, M. Dziadosz, A.A. Gorzawski, L. K. Grob, E.B. Holzer, A. Lechner, R. Schmidt, M. Valette, D. Valuch, D. Wollmann
    CERN, Geneva, Switzerland
 
  Micrometer sized particles entering the LHC beam (the so-called Unidentified Falling Objects or UFOs) are a known cause of localized beam losses since the beginning of high intensity beam operation, however the origin of these particles is not fully known. Their effect limits LHC availability by causing premature dumps due to excessive beam losses and occasionally even magnet quenches. This could become an important limitation for future accelerators such as the High Luminosity upgrade of the LHC (HL-LHC) and the Future Circular Collider (FCC). The dynamics of these UFOs was investigated in two dedicated experiments. In the first experiment, it was shown that the transverse movements of these particles can be studied by observing bunch-by-bunch losses from bunches with different horizontal and vertical emittances. In the second experiment, UFO-like events around the 16L2 interconnect in the LHC, which has seen intense UFO activity in 2017, were studied with the above method. This paper summarizes the results of both experiments.  
slides icon Slides THYGBD2 [1.361 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBD2  
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THPAF017 Improvement of RF Field Phase and Amplitude Errors Simulations in TraceWin Code cavity, simulation, linac, diagnostics 2983
 
  • D. Uriot
    IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
 
  Funding: This work is supported by the European Atomic Energy Community's (EURATOM) H2020 Programme under grant agreement n°662186 (MYRTE project)
RF field phase and amplitude errors are usually not correctly simulated and it is a serious problem especially when in high intensity linear accelerators, the main losses are due to particle leaving the beam acceptance. This new development implemented in TraceWin fixes this issue. The objective is to improve the longitudinal beam dynamics simulation methods, by including more close-to-real models for the cavities tuning procedure. By this way, clear distinction should be done between static and dynamic errors and longitudinal diagnostics accuracy can be clearly defined according to beam dynamics results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF017  
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THPMF015 Lifetime and Beam Losses Studies of Partially Strip Ions in the SPS (129Xe39+) vacuum, injection, factory, electron 4070
 
  • S. Hirlaender, R. Alemany-Fernández, H. Bartosik, N. Biancacci, T. Bohl, S. Cettour Cave, K. Cornelis, B. Goddard, V. Kain, M.W. Krasny, M. Lamont, D. Manglunki, G. Papotti, M. Schaumann, F. Zimmermann
    CERN, Geneva, Switzerland
  • K. Kroeger
    FSU Jena, Jena, Germany
  • V.P. Shevelko
    LPI RAS, Moscow, Russia
  • T. Stöhlker, G. Weber
    IOQ, Jena, Germany
 
  The CERN multipurpose Gamma Factory proposal relies on using Partially Stripped Ion (PSI) beams, instead of electron beams, as the drivers of its light source. If such beams could be successfully stored in the LHC ring, fluxes of the order of 1017 photons/s, in the gamma-ray energy domain between 1 MeV and 400 MeV could be achieved. This energy domain is out of reach for the FEL-based light sources as long as the multi TeV electron beams are not available. The CERN Gamma Factory proposal has the potential of increasing by 7 orders of magnitude the intensity limits of the present Inverse Compton Scattering sources. In 2017 the CERN accelerator complex demonstrated its flexibility by producing a new, xenon, ion beam. The Gamma Factory study group, based on this achievement, requested special studies. Its aim was to inject and to accelerate, in the SPS, partially stripped xenon ions Xe39+ measure their life time, and determine the relative strength of the processes responsible for the PSI beam losses. This study, the results of which are presented in this contribution, was an initial step in view of the the future studies programmed for 2018 with lead PSI beams.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF015  
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FRXGBD1 Reliability and Availability of Particle Accelerators: Concepts, Lessons, Strategy operation, luminosity, collider, kicker 5014
 
  • A. Apollonio, L. Ponce, O. Rey Orozko, R. Schmidt, A.P. Siemko, B. Todd, J.A. Uythoven, A.P. Verweij, D. Wollmann, M. Zerlauth
    CERN, Geneva, Switzerland
 
  This paper will present the results and latest status of an extensive effort to analyse and improve the reliability and availability of the LHC. After the introduction of basic concepts and definitions, the paper reviews the performance of the LHC in 2015-2017. A direct comparison of the luminosity production years 2016 and 2017 is presented, with a focus on the main differences in the observed failure modes. Based on the lessons learnt in this time window, expectations for the performance during future LHC runs are discussed. In particular, the thought process for the evaluation of the possible full energy exploitation of the LHC is described, considering relevant factors such as the expected availability loss and the risk associated to magnet training.  
slides icon Slides FRXGBD1 [7.095 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-FRXGBD1  
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