06 Instrumentation, Controls, Feedback & Operational Aspects

T17 Alignment and Survey

Paper Title Page
TUPC115 Vibration Stabilization for a Cantilever Magnet Prototype at the Subnanometer Scale 1335
 
  • L. Brunetti, B. Bolzon, N. Geffroy, A. Jeremie
    IN2P3-LAPP, Annecy-le-Vieux
  • A. Badel, B. Caron, J. Lottin
    SYMME, Annecy-le-Vieux
 
  In the future linear colliders, the size of the beams is in the nanometer range, which requires stabilization of the final magnets before the interaction point. In order to guarantee the desired luminosity, an absolute displacement lower than 1/3 of the beam size, above a few hertz, has to be obtained. This paper describes an adapted instrumentation, the developed feedback loops dedicated to the active compensation and an adapted modelling able to simulate the behaviour of the structure. The obtained results at the subnanometer scale at the free end of a cantilever magnet prototype with a combination of the developed active compensation method and a commercial active isolation system are described.  
TUPC116 Field Characterization of XFEL Quadrupole Magnets 1338
 
  • A. Hedqvist, H. Danared, F. Hellberg
    MSL, Stockholm
  • J. Pflueger
    DESY, Hamburg
 
  The European X-ray free electron laser (XFEL) will be one of the most advanced light source facilities in Europe and produce high intensity laser light of wavelengths down to 0.1 nm*. The laser light is produced and amplified by electrons moving through long undulator systems, each consisting of several 5 m long segments. After each undulator segment an adjustable quadrupole magnet is placed to focus the electron beam. For optimum control of the laser light the centre of the quadrupoles need to be positioned along a straight line with an accuracy of 0.001 mm which only can be reached by beam based alignment (BBA). Prior to the BBA procedure the magnets need to be aligned along the beam path, therefore the centre position of the magnet has to be determined relative to fiducials placed on the magnet body with an accuracy of approximately 0.01 mm. A rotating coil system has been set up at the Manne Siegbahn Laboratory to characterize the magnetic field between the four magnetic poles and to measure the stability of the magnetic centre. The accuracy of this instrument and procedures of how to fiducialize the magnetic centre are presented.

*European XFEL technical design report, edited by M. Altarelli et. al., DESY 2006.

 
TUPC117 Beam Based Alignment of Quadrupole Triplets by Use of MATLAB Based Modeling 1341
 
  • O. Kopitetzki, D. Schirmer, G. Schmidt, K. Wille
    DELTA, Dortmund
 
  A new beam based method is introduced to measure the transversal shifts of quadrupole magnets in relation to each other within triplet structures. The displacements of the quadrupole magnets can be calculated by quadrupole strength variation in combination with a simulation of the orbit distortions utilizing a MATLAB based model for beam optics. A local smoothing of the quadrupole alignment can be achieved with accuracy better than those of geodetic surveys. Results are presented and compared with data from geodetic surveys.  
TUPC118 First Data from the Linear Collider Alignment and Survey Project (LiCAS) 1344
 
  • A. Reichold, T. Handford, L. A. Rainbow, M. Tacon, C. Uribe Estrada, D. Urner, S. Q. Yang
    OXFORDphysics, Oxford, Oxon
  • P. J. Brockill, S. Cohen, J. Dale, M. Dawson, M. Jones, G. Moss, R. Wastie
    JAI, Oxford
  • G. Grzelak
    Warsaw University, Warsaw
  • J. Prenting, M. Schloesser
    DESY, Hamburg
 
  The LiCAS project has developed a prototype robotic survey system for rapid and highly accurate surveying of long linear accelerator tunnel networks. It is aimed at the survey of the reference network for the International Linear Collider (ILC). This Rapid Tunnel Reference Surveyor (RTRS) is designed to be an R\&D instrument for evaluating the potential performance of the RTRS concept and its survey technology. The prototype has been commissioned in a test tunnel at DESY with initial calibrations and measurements ongoing. We will report on the results obtained so far and present conclusions for the design of an RTRS suitable for the ILC.  
TUPC119 Corrector Based Determination of Quadrupole Centres 1347
 
  • M. Sjöström, M. Eriksson, L.-J. Lindgren, E. J. Wallén
    MAX-lab, Lund
 
  A corrector magnet based method to determine the quadrupole magnet centres for storage rings has been tested on the MAX III synchrotron light source. The required corrector magnet strengths for the corrected beam orbit are used to determine the quadrupole magnet centre positions. This method is the most effective for an optimal distribution of beam position monitors and corrector magnets in the storage ring and will be used as a basis for the MAX IV storage rings.  
TUPC121 Nanometre Precision Interferometric Stability Monitoring Systems for Key Accelerator Components 1350
 
  • P. A. Coe, A. Reichold, D. Urner
    OXFORDphysics, Oxford, Oxon
  • M. S. Warden
    JAI, Oxford
 
  The MONALISA group develops novel, accurate, nanometre resolution, interferometric systems to monitor relative motions between key accelerator components. We use cost-effective technology developed for the telecommunications market, providing readily scalable, adaptable solutions. Key magnets and diagnostics in the beam-delivery section of the International Linear Collider (ILC) will need to maintain stable relative positions. In particular, the final focus quadrupole magnets require nanometre level stability. Even greater stability requirements will be placed on components for the Compact Linear Accelerator (CLIC). Interferometers provide the only means of monitoring relative positions over long timescales, at the nanometre and sub-nanometre level. We are working to improve our measurement resolution using an optical frequency reference obtained by locking the second harmonic of an ultra-narrow linewidth 1560 nm fibre laser to a D2 transition in Rubidium-87. The latest results from this system tested on novel design, fibre-coupled, evacuated interferometers will be presented.  
TUPC122 Feedback Corrections for Ground Motion Effects at ATF2 1353
 
  • Y. Renier, P. Bambade
    LAL, Orsay
 
  Ground motion will over time produce beam misalignments and size increases at the IP of the ATF2 beam line. The spatial and temporal characteristics of the vibrations measured on the site have been studied and model parameters have been fitted to allow reliably simulating the effects induced on the beam. A feedback loop to minimise the residual beam motion at the IP is considered, based on optimising the coefficients of a PID controller on both short and long time-scales.