Author: Corsini, R.
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WEOBB02 Status of Wakefield Monitor Experiments at the CLIC Test Facility 2099
  • R.L. Lillestøl, E. Adli, J. Pfingstner
    University of Oslo, Oslo, Norway
  • N. Aftab, S. Javeed
    PINSTECH, Islamabad, Pakistan
  • R. Corsini, S. Döbert, W. Farabolini, A. Grudiev, W. Wuensch
    CERN, Geneva, Switzerland
  For the very low emittance beams in CLIC, it is vital to mitigate emittance growth which leads to reduced luminosity in the detectors. One factor that leads to emittance growth is transverse wakefields in the accelerating structures. In order to combat this the structures must be aligned with a precision of a few um. For achieving this tolerance, accelerating structures are equipped with wakefield monitors that measure higher-order dipole modes excited by the beam when offset from the structure axis. We report on such measurements, performed using prototype CLIC accelerating structures which are part of the module installed in the CLIC Test Facility 3 (CTF3) at CERN. Measurements with and without the drive beam that feeds rf power to the structures are compared. Improvements to the experimental setup are discussed, and finally remaining measurements that should be performed before the completion of the program are summarized.  
slides icon Slides WEOBB02 [2.928 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOBB02  
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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
  • J. Roberts, P. Burrows, G.B. Christian, C. Perry
    JAI, Oxford, United Kingdom
  • A. Andersson, R. Corsini, P.K. Skowroński
    CERN, Geneva, Switzerland
  • A. Ghigo, F. Marcellini
    INFN/LNF, Frascati (Roma), Italy
  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.
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
  • L. Malina, R. Corsini, D. Gamba, T. Persson, P.K. Skowroński
    CERN, Geneva, Switzerland
  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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THPMB046 Status and Plans for Completion of the Experimental Programme of the Clic Test Facility Ctf3 3347
  • P.K. Skowroński, R. Corsini, S. Döbert, W. Farabolini, D. Gamba, L. Malina, T. Persson, F. Tecker
    CERN, Geneva, Switzerland
  • W. Farabolini
    CEA/DSM/IRFU, France
  • D. Gamba
    JAI, Oxford, United Kingdom
  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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THPOR031 Beam-Loading Effect on Breakdown Rate in High-Gradient Accelerating Structures 3848
  • F. Tecker, T. Argyropoulos, N. Catalán Lasheras, R. Corsini, A. Degiovanni, D. Gamba, J. Giner Navarro, A. Grudiev, G. McMonagle, J.L. Navarro Quirante, R. Rajamaki, E. Senes, I. Syratchev, B.J. Woolley, W. Wuensch
    CERN, Geneva, Switzerland
  • T. Argyropoulos, J. Giner Navarro
    IFIC, Valencia, Spain
  • A. Degiovanni, J.L. Navarro Quirante
    ADAM, Geneva, Switzerland
  • D. Gamba
    JAI, Oxford, United Kingdom
  • R. Rajamaki
    Aalto University, School of Science and Technology, Aalto, Finland
  • E. Senes
    Torino University, Torino, Italy
  • J. Tagg
    National Instruments Switzerland, Ennetbaden, Switzerland
  The Compact Linear Collider (CLIC) study for a future electron-positron collider with a center-of-mass energy up to 3 TeV aims for an accelerating gradient of 100 MV/m. The gradient is limited by RF breakdowns, and the luminosity requirements impose a limit on the admissible RF breakdown rate. RF testing of 12 GHz structure prototypes has shown that gradients in excess of 100 MV/m can be reached with the required breakdown rate. However at CLIC, the structures will be operated with significant beam-loading, modifying the field distribution inside. The effect of the beam-loading must be well understood but has not been previously measured. The commissioning and operation of an experiment to measure the effect of beam-loading on breakdown rate and the measurement results are presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR031  
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THPOR032 Effect and Optimisation of Non-Linear Chromatic Aberrations of the CLIC Drive Beam Recombination at CTF3 3852
  • D. Gamba, R. Corsini, P.K. Skowroński, F. Tecker
    CERN, Geneva, Switzerland
  • P. Burrows
    JAI, Oxford, United Kingdom
  • P. Burrows
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  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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