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Sapinski, M.

Paper Title Page
MOPD53 Quench Protection with LHC Beam Loss Monitors 198
  • M. Sapinski, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, C. Kurfuerst, A. Priebe, C. Zamantzas
    CERN, Geneva

To prevent from beam-induced quenches of the superconducting magnets a system of about 4000 beam loss detectors is installed on the magnets cryostats. These detectors, being ionization chambers, measure the particle shower starting inside the magnet. Examples of simulations linking the heat deposited in the superconducting coils with signals in the ionization chambers are presented. A comparison of the simulations to the data is done. Limits of the present system are discussed.

MOPD61 Carbon Fiber Damage in Particle Beam 231
  • M. Sapinski, B. Dehning, A. Guerrero, T. Kroyer, M. Meyer
    CERN, Geneva

Carbon fibers are commonly used as moving targets in the beam wire scanners. The heating of the fiber due to energy loss of the particles traveling through is simulated with Geant4. Heating induced by the beam electromagnetic field is estimated with ANSYS. The heat transfer and sublimation processes are modeled. Due to the model nonlinearity a numerical approach based on discretization of the wire movement is used to solve it for particular beams. Radiation damage to the fiber is estimated with SRIM. The model is tested with available SPS and LEP data and a dedicated damage test on SPS beam is performed followed by post-mortem analysis of the wire remnants. Prediction for the LHC beams is made.

MOPD63 Development, Characterisation and Performance of the LHC Beam Loss Monitoring System 240
  • A. Nordt, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, D.K. Kramer, E. Lebbos, M. Sapinski, M. Stockner, C. Zamantzas
    CERN, Geneva

The LHC beam loss monitoring system is a safety critical system and ~ 4000 monitors are installed around the ring in order to prevent the superconducting magnets from quenches and protect the machine components from damage. Two different types of beam loss monitors are used: an ionization chamber (IC) and a secondary emission monitor (SEM). The response functions and expected signals have been simulated using Geant4 as well as FLUKA and have been validated and verified with measurements. The Geant4 model of the beam loss monitors has been tested with protons, gammas, neutrons, muon and mixed field beams for steady state and instantaneous losses. Results from the simulations compared to measurement results will be presented. The expected signals for several events (e.g. direct beam impact on collimators, over-injection, high intensity injection) have been checked against real data being taken during the LHC runtime in 2009 and 2010. The very good performance of the system and the agreement with previous simulations will be shown and discussed.

MOPD48 Leakage from LHC Dump Protection System 176
  • C. Bracco, R.W. Assmann, W. Bartmann, C. Boucly, R. Bruce, E. Carlier, B. Dehning, B. Goddard, E.B. Holzer, M. Meddahi, A. Nordt, S. Redaelli, A. Rossi, M. Sapinski, J.A. Uythoven, D. Wollmann
    CERN, Geneva

A single-sided mobile diluter (TCDQ) and a horizontal secondary collimator(TCSG) are installed in the extraction region of the LHC to protect the downstream elements from damage in case of asynchronous beam dump. These collimators have to be precisely setup to shield the arc aperture at 450 GeV, the triplet apertures and the tungsten tertiary collimators (TCT) at the low-beta collision points. During the LHC beam commissioning, several machine protection tests were carried out to validate collimator setup and hierarchy at different beam energies and intensities. The outcomes of these measurements are presented in this paper together with the results of particle tracking simulations for asynchronous beam dump. These studies allowed to quantify the leakage expected from dump protection collimators to the downstream elements, and to validate the system performance towards higher beam intensity.

WEO1C01 Commissioning and Optimization of the LHC BLM System 487
  • E.B. Holzer, B. Dehning, E. Effinger, J. Emery, C.F. Hajdu, S. Jackson, C. Kurfuerst, A. Marsili, M. Misiowiec, E. Nebot Del Busto, A. Nordt, C. Roderick, M. Sapinski, C. Zamantzas
    CERN, Geneva
  • V. Grishin
    IHEP Protvino, Protvino, Moscow Region

Due to rapid progress with the LHC commissioning in 2010 set-up beam intensities were soon surpassed and damage potential reached. One of the key systems for machine protection is the beam loss monitoring (BLM) system. Around 4000 monitors are installed at likely or critical loss locations. Each monitor has 384 associated beam abort thresholds (12 integrated loss durations from 40 us to 83 s for 32 energy intervals). A single integrated loss over threshold on a single monitor aborts the beam. Simulations of deposited energy, critical energy deposition for damage or quench and BLM signal response backed-up by control measurements determined the initial threshold settings. The commissioning and optimization of the BLM system is presented. Test procedures were used to verify the machine protection functionalities and optimize the system parameters. Dedicated beam tests and accidental magnet quenches were used to fine-tune threshold settings. The most significant changes to the BLM system during the 2010 run concerned the injection, the collimation and the beam dump region, where hardware changes and threshold increases became necessary to accommodate for increasing beam intensity.


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