Author: Redaelli, S.
Paper Title Page
MOMMU003 Aperture Meter for the Large Hadron Collider 70
  • G.J. Müller, K. Fuchsberger, S. Redaelli
    CERN, Geneva, Switzerland
  The control of the high intensity beams of the CERN Large Hadron Collider (LHC) is particular challenging and requires a good modeling of the machine and monitoring of various machine parameters. During operation it is crucial to ensure a minimal distance between the beam edge and the aperture of sensitive equipment, e.g. the superconducting magnets, which in all cases must be in the shadow of the collimators that protect the machine. Possible dangerous situations must be detected as soon as possible. In order to provide the operator with information about the current machine bottlenecks an aperture meter application was developed based on the LHC online modeling toolchain. The calculation of available free aperture takes into account the best available optics and aperture model as well as the relevant beam measurements. This paper describes the design and integration of this application into the control environment and presents results of the usage in daily operation and from validation measurements.  
slides icon Slides MOMMU003 [0.565 MB]  
poster icon Poster MOMMU003 [0.694 MB]  
MOPMN018 Toolchain for Online Modeling of the LHC 277
  • G.J. Müller, X. Buffat, K. Fuchsberger, M. Giovannozzi, S. Redaelli, F. Schmidt
    CERN, Geneva, Switzerland
  The control of high intensity beams in a high energy, superconducting machine with complex optics like the CERN Large Hadron Collider (LHC) is challenging not only from the design aspect but also for operation. To support the LHC beam commissioning, operation and luminosity production, efforts were recently devoted towards the design and implementation of a software infrastructure aimed to use the computing power of the beam dynamics code MADX-X in the framework of the Java-based LHC control and measurement environment. Alongside interfacing to measurement data as well as to settings of the control system, the best knowledge of machine aperture and optic models is provided. In this paper, we present the status of the toolchain and illustrate how it has been used during commissioning and operation of the LHC. Possible future implementations are also discussed.  
poster icon Poster MOPMN018 [0.562 MB]  
WEPMU020 LHC Collimator Controls for a Safe LHC Operation 1104
  • S. Redaelli, R.W. Assmann, M. Donzé, R. Losito, A. Masi
    CERN, Geneva, Switzerland
  The beam stored energy at the Large Hadron Collider (LHC) will be up to 360 MJ, to be compared with the quench limit of super-conducting magnets of a few mJ per cm3 and with the damage limit of metal of a few hundreds kJ. The LHC collimation system is designed to protect the machine against beam losses and consists of 108 collimators, 100 of which are movable, located along the 27 km long ring and in the transfer lines. Each collimator has two jaws controlled by four stepping motors to precisely adjust collimator position and angle with respect to the beam. Stepping motors have been used to ensure high position reproducibility. LVDT and resolvers have been installed to monitor in real-time at 100 Hz the jaw positions and the collimator gaps. The cleaning performance and machine protection role of the system depend critically on the accurate jaw positioning. A fully redundant survey system has been developed to ensure that the collimators dynamically follow optimum settings in all phases of the LHC operational cycle. Jaw positions and collimator gaps are interlocked against dump limits defined redundantly as functions of the time, of the beam energy and of the beta* functions that describes the focusing property of the beams. In this paper, the architectural choices that guarantee a safe LHC operation are presented. Hardware and software implementations that ensure the required reliability are described. The operational experience accumulated so far is reviewed and a detailed failure analysis that show the fulfillment of the machine protection specifications is presented.  
FRBHAULT01 Feed-forward in the LHC 1302
  • M. Pereira, X. Buffat, K. Fuchsberger, M. Lamont, G.J. Müller, S. Redaelli, R.J. Steinhagen, J. Wenninger
    CERN, Geneva, Switzerland
  The LHC operational cycle is comprised of several phases such as the ramp, the squeeze and stable beams. During the ramp and squeeze in particular, it has been observed that the behaviour of key LHC beam parameters such as tune, orbit and chromaticity are highly reproducible from fill to fill. To reduced the reliance on the crucial feedback systems, it was decided to perform fill-to-fill feed-forward corrections. The LHC feed-forward application was developed to ease the introduction of corrections to the operational settings. It retrieves the feedback system's corrections from the logging database and applies appropriate corrections to the ramp and squeeze settings. The LHC Feed-Forward software has been used during LHC commissioning and tune and orbit corrections during ramp have been successfully applied. As a result, the required real-time corrections for the above parameters have been reduced to a minimum.  
slides icon Slides FRBHAULT01 [0.961 MB]