Author: Redaelli, S.
Paper Title Page
TUPZ001 90 m Optics Commissioning 1795
 
  • S. Cavalier
    LAL, Orsay, France
  • H. Burkhardt, M. Fitterer, G.J. Müller, S. Redaelli, R. Tomás, G. Vanbavinckhove, J. Wenninger
    CERN, Geneva, Switzerland
 
  Special β* = 90 m optics have been developed for the two very high luminosity insertions of the LHC, as a first step towards to allow for very low angle precision measurements of the proton-proton collisions in the LHC. These optics were developed to be compatible with the standard LHC injection and ramp optics. The target value of β* = 90 m is reached by an un-squeeze from the injection β* = 11 m. We describe the implementation of this optics in the LHC and the first experience in the commissioning of these optics.  
 
TUPZ006 Aperture Determination in the LHC Based on an Emittance Blowup Technique with Collimator Position Scan 1810
 
  • R.W. Assmann, R. Bruce, M. Giovannozzi, G.J. Müller, S. Redaelli, F. Schmidt, R. Tomás, J. Wenninger, D. Wollmann
    CERN, Geneva, Switzerland
  • M. Alabau
    IFIC, Valencia, Spain
 
  A new method to determine the LHC aperture was proposed. The new component is a collimator scan technique that refers the globally measured aperture limit to the shadow of the primary collimator, expressed in σs of rms beam size. As a by-product the BLM response to beam loss is quantified. The method is described and LHC measurement results are presented.  
 
TUPZ028 Beam Based Optimization of the Squeeze at the LHC 1867
 
  • X. Buffat
    EPFL, Lausanne, Switzerland
  • M. Lamont, S. Redaelli, J. Wenninger
    CERN, Geneva, Switzerland
 
  The betatron squeeze is a critical operational phase for the LHC because it is carried out at top energy, with the maximum stored energy and with reduced aperture margins in the superconducting triplets. A stable operation with minimum beam losses must be achieved in order to ensure a safe and efficient operation. The operational experience at the LHC showed that this is possible. The operation in 2010 is reviewed. In particular, orbit, tune and chromaticity measurements are investigated and correlated to beam losses. Different optimizations are then proposed towards a more efficient and robust operation. The improvements obtained for the operation in 2011 are presented.  
 
TUPZ030 Simulation of Linear Beam Parameters to Minimize the Duration of the Squeeze at the LHC 1873
 
  • X. Buffat
    EPFL, Lausanne, Switzerland
  • G.J. Müller, S. Redaelli, M. Strzelczyk
    CERN, Geneva, Switzerland
 
  The betatron squeeze allows to increase the luminosity of a collider by reducing the β function at the interaction points. This operation has shown to be very critical in previous colliders. In this state of mind, the squeezing was performed extremely safely during the first year of operation of the Large Hadron Collider, at the expense of the duration of the process. As the turnaround time is a relevant parameter for the integrated luminosity, a squeeze of shorter duration is proposed for 2011 and further. MadX simulation of linear beam parameters based on settings extracted from the LHC control system are used to justify the proposal. Further optimization of the squeeze setting generation is also discussed.  
 
MOPO011 The First 1 1/2 Years of TOTEM Roman Pot Operation at LHC 502
 
  • M. Deile, G.H. Antchev, R.W. Assmann, I. Atanassov, V. Avati, J. Baechler, R. Bruce, M. Dupont, K. Eggert, B. Farnham, J. Kaspar, F. Lucas Rodríguez, J. Morant, H. Niewiadomski, X. Pons, E. Radermacher, S. Ravat, F. Ravotti, S. Redaelli, G. Ruggiero, H. Sabba, M. Sapinski, W. Snoeys, G. Valentino, D. Wollmann
    CERN, Geneva, Switzerland
  • R. Appleby
    UMAN, Manchester, United Kingdom
 
  Since the LHC running season 2010, the TOTEM Roman Pots (RPs) are fully operational and serve for collecting elastic and diffractive proton-proton scattering data. Like for other moveable devices approaching the high intensity LHC beams, a reliable and precise control of the RP position is critical to machine protection. After a review of the RP movement control and position interlock system, the crucial task of alignment will be discussed.  
 
THPZ026 Collimation Dependent Beam Lifetime and Loss Rates in the LHC 3744
 
  • D. Wollmann, R.W. Assmann, R. Bruce, F. Burkart, M. Cauchi, D. Deboy, S. Redaelli, A. Rossi, G. Valentino
    CERN, Geneva, Switzerland
 
  The four primary collimators in each LHC beam define the smallest aperture. Particles with high betatron amplitudes or momentum offset will therefore hit first a primary collimator. The instantaneous particle loss rate at primary collimators is an important measure for the global lifetime of the beams and a major ingredient to identify collimation induced performance limitations in the LHC. These loss rates have been measured during a number of LHC fills, featuring both "good" fills with high luminosity and "bad" fills with beam instabilities. The beam lifetime at the collimators was then calculated from this data for different cases. The results are presented and interpreted within this paper.  
 
THPZ029 Principles for Generation of Time-dependent Collimator Settings during the LHC Cycle 3753
 
  • R. Bruce, R.W. Assmann, S. Redaelli
    CERN, Geneva, Switzerland
 
  The settings of the LHC collimators have to be changed during the cycle of injection, ramp and squeeze to account for variations in the orbit, beam size and normalized distance to the beam center. We discuss the principles for how the settings are calculated and show a software tool that computes them as time-dependent functions from beam-based data and theoretical optics models.  
 
THPZ030 Halo Scrapings with Collimators in the LHC 3756
 
  • F. Burkart, R.W. Assmann, R. Bruce, M. Cauchi, D. Deboy, S. Redaelli, A. Rossi, G. Valentino, D. Wollmann
    CERN, Geneva, Switzerland
  • L. Lari
    IFIC, Valencia, Spain
 
  The population of the beam halo has been measured in the LHC with beam scraping experiments. Primary collimators of the LHC collimation system were used to scrape the beam halo at different statuses of the machine (injection, top energy, separated and colliding beams). In addition these measurements were used to calibrate the beam loss monitor signals to loss rates at the primary collimators. Within this paper the halo scraping method, the measured halo distribution and the calibration factors are presented and compared to theoretical predictions.  
 
THPZ031 Acoustic Measurements in the Collimation Region of the LHC 3759
 
  • D. Deboy, R.W. Assmann, C. Baccigalupi, F. Burkart, M. Cauchi, C.S. Derrez, J. Lendaro, A. Masi, S. Redaelli, G. Spiezia, D. Wollmann
    CERN, Geneva, Switzerland
 
  The LHC accelerator at CERN has the most advanced collimation system ever being installed. The collimators intercept unavoidable particle losses and therefore are essential to avoid beam induced quenches of the superconducting magnets. In addition, they provide passive machine protection against mis-kicked beams. During material robustness tests on a LHC collimator prototype in 2004 and 2006, vibration and acoustic measurements have shown that a beam impact detection system should be feasible using accelerometers and microphones as sensors in the LHC. Recently, such sensors have been installed close to the primary collimators in the LHC tunnel. First analyses of raw data show that the system is sensitive enough to detect beam scraping on collimators. Therefore, the implementation of a sophisticated acoustic monitoring system is under investigation. It may be useful not only to detect beam impacts on primary collimators in case of failure, but also to derive further information on beam losses that occur during regular operation. This paper gives an overview on the recent installation, results of the acoustic measurements made at the LHC, and future plans.  
 
THPZ033 Operational Experience and Performance of the LHC Collimator Controls System 3765
 
  • S. Redaelli, A. Masi
    CERN, Geneva, Switzerland
 
  In order to handle stored energies up to 360 MJ, the LHC relies on a collimation system that consists of 100 movable collimators. Compared to other accelerator, the complexity of this system is unique: more than 400 motors and about 600 interlocked position sensors must be controlled in all the machine phases in order to ensure the cleaning and machine protection roles of the system. In this paper, the controls system and the setting management are presented and the operational experience accumulated in the 2 first years of operation is discussed, focussing in particular on failure and availability statistics during the LHC operation.  
 
THPZ034 Semi-automatic Beam-based Alignment Algorithm for the LHC Collimation System 3768
 
  • G. Valentino, R.W. Assmann, S. Redaelli, N.J. Sammut, D. Wollmann
    CERN, Geneva, Switzerland
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
 
  Full beam-based alignment of the LHC collimation system was a lengthy procedure as the collimators were set up manually. A yearly alignment campaign has been sufficient for now, although in future this may lead to a decrease in the cleaning efficiency if machine parameters such as the beam orbit drift over time. Automating the collimator setup procedure can allow for more frequent alignments, therefore reducing this risk. This paper describes the design and testing of a semi-automatic algorithm as a first step towards a fully automatic setup. Its implementation in the collimator control software and future plans are described.  
 
THPZ035 Comparison of LHC Collimation Setups with Manual and Semi-automatic Collimator Alignment 3771
 
  • G. Valentino, R.W. Assmann, R. Bruce, F. Burkart, M. Cauchi, D. Deboy, S. Redaelli, A. Rossi, N.J. Sammut, D. Wollmann
    CERN, Geneva, Switzerland
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
 
  The LHC collimation system beam-based alignment procedure has recently been upgraded to a semi-automatic process in order to increase its efficiency. In this paper, we describe the parameters used to measure the accuracy, stability and performance of the beam-based alignment of the LHC collimation system. This is followed by a comparison of the results at 450 GeV and 3.5 TeV with (1) a manual alignment and (2) with the results for semi-automatic alignment.  
 
THPZ027 First Beam Results for a Collimator with In-jaw Beam Position Monitors 3747
 
  • D. Wollmann, O. Aberle, R.W. Assmann, A. Bertarelli, C.B. Boccard, R. Bruce, F. Burkart, M. Cauchi, A. Dallocchio, D. Deboy, M. Gasior, O.R. Jones, S. Redaelli, A. Rossi, G. Valentino
    CERN, Geneva, Switzerland
 
  With more than 100 collimators the LHC has the most complex collimation system ever installed in an accelerator. The beam-based setup time of the system was a non-negligible factor during the commissioning of the LHC. In addition if the particle orbit at a collimator goes out of tolerance, this collimator needs to be setup again. To reduce the required setup time for the collimation system and to obtain the tight tolerances required for the LHC operation with small beta* and high beam energy, a new collimator design is being developed that integrates a beam position monitor (BPM) into the jaws of the collimator. A prototype of such a phase-II LHC collimator was installed in the SPS at CERN for the 2010 run. In this paper we present the first experimental results from the beam tests performed.