Author: Catalan-Lasheras, N.     [Catalán Lasheras, N.]
Paper Title Page
WEPRB058 Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures 2940
SUSPFO091   use link to see paper's listing under its alternate paper code  
 
  • D. Banon-Caballero
    IFIC, Valencia, Spain
  • N. Catalán Lasheras, K. T. Szypula, W. Wuensch
    CERN, Geneva, Switzerland
  • A. Faus-Golfe
    LAL, Orsay, France
  • B. Gimeno
    UVEG, Burjasot (Valencia), Spain
 
  Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB058  
About • paper received ※ 27 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB059 Dark Current Analysis at CERN’s X-band Facility 2944
 
  • D. Banon-Caballero, M. Boronat, V. Sánchez Sebastián, A. Vnuchenko
    IFIC, Valencia, Spain
  • N. Catalán Lasheras, S. Pitman, M. Widorski, W. Wuensch, V. del Pozo Romano
    CERN, Meyrin, Switzerland
  • A. Faus-Golfe
    LAL, Orsay, France
  • B. Gimeno
    UVEG, Burjasot (Valencia), Spain
  • T.G. Lucas, M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
  • W.L. Millar
    Lancaster University, Lancaster, United Kingdom
  • J. Paszkiewicz
    University of Oxford, Oxford, United Kingdom
 
  Dark current is particularly relevant during operation in high-gradient linear accelerators. Resulting from the capture of field emitted electrons, dark current produces additional radiation that needs to be accounted for in experiments. In this paper, an analysis of dark current is presented for four accelerating structures that were tested and conditioned in CERN’s X-band test facility for CLIC. The dependence on power, and therefore on accelerating gradient, of the dark current signals is presented. The Fowler-Nordheim equation for field emission seems to be in accordance with the experimental data. Moreover, the analysis shows that the current intensity decreases as a function of time due to conditioning, but discrete jumps in the dark current signals are present, probably caused by breakdown events that change the emitters’ location and intensity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB059  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB063 Connection of 12 GHz High Power RF from the XBOX 1 High Gradient Test Stand to the CLEAR Electron LINAC 2960
 
  • A.V. Edwards
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • N. Catalán Lasheras, S. Gonzalez Anton, G. McMonagle, S. Pitman, B.J. Woolley, V. del Pozo Romano
    CERN, Meyrin, Switzerland
 
  A new RF system is being established at XBOX1 to drive two §I{100}{MV/m} CLIC structures in the CLEAR electron linac. In the past, these structures had been powered by RF from PET structures excited by a drive beam. This drive beam is no longer available. The upgrade will reroute power from the §I{50}{MW} klystron and pulse compressor which was previously used to power the structure in XBOX1. During the upgrade, the LLRF system will be optimised to improve the modulation of the output signals and down-mixing of the returning signals to obtain accurate phase and amplitude information. The design of the improved LLRF and software, along with phase noise measurements and comparisons with the old system are made in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB063  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEPRB064 High Power Conditioning of X-Band Variable Power Splitter and Phase Shifter 2964
 
  • V. del Pozo Romano, H. Bursali, N. Catalán Lasheras, A. Grudiev, S. Pitman, I. Syratchev
    CERN, Geneva, Switzerland
  • C. Serpico
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • M. Volpi
    The University of Melbourne, Melbourne, Victoria, Australia
 
  The three X-band test facilities currently at CERN aim at qualifying CLIC structures prototypes but are also exten- sively used to qualify X-band components operation at high power. In order to upgrade one of the facilities from a single test line to a double test line facility, a high power variable splitter and variable phase shifter have been designed and manufactured at CERN. They have been power tested, first in a dedicated test and also in their final configuration, to en- sure stable power operation before installing them together with an accelerating structure. In this paper, we broadly describe the RF and mechanical design, manufacturing and low power measurements agreement with simulations. We report the high power qualification of both components and their suitability to be used in existing and planned X-band facilities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB064  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPRB071 Beam-Based Measurements on Two ±12.5 kV Inductive Adders, together with Striplines, for CLIC Damping Ring Extraction Kickers 3970
 
  • J. Holma, M.J. Barnes, M. Carlà, N. Catalán Lasheras, Y. Papaphilippou
    CERN, Meyrin, Switzerland
  • U. Iriso, Z. Martí, F. Pérez, M. Pont
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
 
  The CLIC study is investigating the technical feasibil-ity of an electron-positron linear collider with high lumi-nosity and a nominal centre-of-mass energy of 3 TeV. Pre-damping rings and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. The DR kicker systems, each of which consists of a set of striplines and two inductive adders, must provide ex-tremely stable field pulses. The DR extraction kicker system is the most demanding: specifications require a field uniformity within ±0.01% and pulses up to 900 ns flattop duration, at ±12.5 kV and 309 A, with ripple and droop of not more than ±0.02 % (±2.5 V), with respect to a reference waveform. Two prototype inductive adders have been designed and built at CERN, and have been tested with prototype striplines installed in the storage ring of the ALBA Synchrotron Light Source, in Spain. The stability of the kicker system, including the modulators, has been evaluated from the beam-based measure-ments and is reported in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB071  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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