01 Circular Colliders

T12 Beam Injection/Extraction and Transport

Paper Title Page
WEPP057 Fitting Algorithms for Optical and Beam Parameters in Transfer Lines with Application to the LHC Injection Line TI2 2647
 
  • E. Benedetto, I. V. Agapov, F. Follin, V. Kain
    CERN, Geneva
 
  As part of the commissioning with beam of the transfer line TI2 from the SPS to the LHC, a series of optics measurements has been conducted. The paper presents the results in terms of Twiss parameters (including the dispersion), emittance and momentum spread obtained from the combination of trajectory and beam profile measurements. Profiting from the redundancy of monitors, there is a possibility of applying different fitting algorithms to retrieve beam parameters and to extract information on the optics of the line. The results from the different fit methods applied to the data will be compared with the expected values and cross-checked with independent measurements with a particular emphasis on the error analysis.  
WEPP058 Optics Measurements and Matching of TT2-TT10 Line for Injection of the LHC Beam in the SPS 2650
 
  • E. Benedetto, G. Arduini, A. Guerrero, D. Jacquet
    CERN, Geneva
 
  A well matched injection in the SPS is very important for preserving the emittance of the LHC beam. The paper presents the algorithms used for the analysis and the results of the optics measurements done in the transfer line TT2-TT10 and in the SPS. The dispersion is computed by varying the beam momentum and recording the offsets at the BPMs, while the Twiss parameters and emittance measurements in TT2-TT10 are performed with beam profile monitors equipped with OTR screens. These results are completed by those obtained with a matching monitor installed in the SPS as a prototype for the LHC. This device makes use of an OTR screen and a fast acquisition system, to get the turn by turn beam profiles right at injection in the ring, from which the beam mismatch is computed and compared with the results obtained in the line. Finally, on the basis of such measurments, a betatron and dispersion matching of TT2-TT10 for injection in the SPS has been performed and successfully put in operation.  
WEPP059 Automatic Post-operational Checks for the LHC Beam Dump System 2653
 
  • E. Gallet, J. Axensalva, V. Baggiolini, E. Carlier, B. Goddard, V. Kain, M. Lamont, N. Magnin, J. A. Uythoven, H. Verhagen
    CERN, Geneva
 
  In order to ensure the required level of reliability of the LHC beam dump system a series of internal post-operational checks after each dump action must be performed. Several data handling and data analysis systems are required internally and at different levels of the LHC control system. This paper describes the data acquisition and analysis systems deployed for post-operational checks, and describes the experience from the commissioning of the equipment where these systems were used to analyse the dump kicker performance.  
WEPP060 Abort Gap Cleaning Using the Transverse Feedback System: Simulation and Measurements in the SPS for the LHC Beam Dump System 2656
 
  • A. Koschik, B. Goddard, W. Höfle, G. Kotzian, D. K. Kramer, T. Kramer
    CERN, Geneva
 
  The critical and delicate process of dumping the beams of the LHC requires very low particle densities within the 3 microseconds of the dump kicker rising edge. High beam population in this so-called 'abort gap' might cause magnet quenches or even damage. Constant refilling due to diffusion processes is expected which will be counter-acted by an active abort gap cleaning system employing the transverse feedback kickers. In order to assess the feasibility and performance of such an abort gap cleaning system, simulations and measurements with beam in the SPS have been performed. Here we report on the results of these studies.  
WEPP061 A Position Monitor for the Aborted Beam in KEKB 2659
 
  • N. Iida, M. Kikuchi, T. Mimashi, K. Mori, M. Tejima
    KEK, Ibaraki
 
  The beams in the KEKB rings are aborted by abort kickers, Lambertson septums and dumps. First the beams are kicked by the abort kickers rapidly in the horizontal direction to outside the beam pipe and are bent slowly in the vertical direction. At the same time horizontal magnetic fields shake the beam to protect the abort window where the kicked beam passes and protect the window from heat by the high current beam. A beam position monitor is installed in front of the dump. We can get some informations of aborted beam by the monitor. In this paper a method for monitoring the beam in the high energy ring at KEKB is described.  
WEPP063 R-matrices of the Fast Beam Extraction Section of AGS 2662
 
  • N. Tsoupas, L. Ahrens, J. W. Glenn, W. W. MacKay, T. Satogata
    BNL, Upton, Long Island, New York
 
  The Fast Beam Extraction (FEB) system of the Alternating Gradient synchrotron (AGS) extracts the beam bunches from AGS into the AGS-to-RHIC (AtR) beam transfer line, and the extracted bunches are injected into the Relativistic Heavy Ion Collider (RHIC) synchrotron. In a particular section of the beam extraction line the beam bunches are transported through the fringe field region of three main AGS magnets. Optical characteristics of this section change with trajectory and momentum. Therefore the calculation of the R-matrices in this part of the extraction line requires special attention. To describe accurately the R-matrices, the magnetic field of the AGS main magnets was measured on the median plane of the AGS magnet in both, the circulating beam region and the fringe field region, where the extracted beam is transported. Using these magnetic field maps we describe the procedure we use to calculate the R-matrices at the beam extraction region. These R-matrices are used to calculate the beam parameters at the starting point of the AtR beam transfer line and the required quadrupole settings to match to RHIC’s acceptance.  
WEPP064 Apertures in the LHC Beam Dump System and Beam Losses during Beam Abort 2665
 
  • T. Kramer, B. Goddard, M. Gyr, A. Koschik, J. A. Uythoven, Th. Weiler
    CERN, Geneva
 
  The LHC beam dump system is used to dispose accelerated protons and ions in a wide energy range from 450 GeV up to 7 TeV. An abort gap of 3 microseconds is foreseen to avoid sweeping particles through the ring aperture. This paper gives a brief overview of the critical apertures in the extraction region and the two beam dump lines, and presents MAD-X tracking studies made to investigate the impact of particles swept through the aperture due to extraction kicker failures or spurious particles within the abort gap.  
WEPP065 Beam Commissioning of the SPS-to-LHC Transfer Line TI 2 2668
 
  • J. A. Uythoven, G. Arduini, R. W. Assmann, N. Gilbert, B. Goddard, V. Kain, A. Koschik, T. Kramer, M. Lamont, V. Mertens, S. Redaelli, J. Wenninger
    CERN, Geneva
 
  The transfer line for the LHC Ring 1 was successfully commissioned with beam in the autumn of 2007. After extraction from the SPS accelerator and about 2.7 km of new transfer line, the beam arrived at the temporarily installed beam dump, about 50 m before the start of the LHC tunnel, without the need of any beam threading. This paper gives an overview of the hardware commissioning period and the actual beam tests carried out. It summarises the results of the beam test optics measurements and the performance of the installed hardware.  
WEPP066 Results from the LHC Beam Dump Reliability Run 2671
 
  • J. A. Uythoven, A. Antoine, E. Carlier, F. Castronuovo, L. Ducimetière, E. Gallet, B. Goddard, N. Magnin, H. Verhagen
    CERN, Geneva
 
  The LHC Beam Dumping System is one of the vital elements of the LHC Machine Protection System and has to operate reliably every time a beam dump request is made. Detailed dependability calculations have been made, resulting in expected rates for the different system failure modes. A 'reliability run' of the system, installed in its final configuration in the LHC, has been made to discover infant mortality problems and to compare the occurrence of the measured failure modes with their calculations.