Author: Siemko, A.P.
Paper Title Page
THPPD026 Splice Resistance Measurements in the LHC Main Superconducting Magnet Circuits by the New Quench Protection System 3557
  • Z. Charifoulline, K. Dahlerup-Petersen, R. Denz, A.P. Siemko, J. Steckert
    CERN, Geneva, Switzerland
  The interconnections between the LHC main magnets are made of soldered joints (splices) of two superconducting cables stabilized by a copper bus bar. After the 2008 LHC incident, caused by a defective interconnection, a new layer of high resolution magnet circuit quench protection (nQPS) has been developed and integrated with the existing systems. It allowed mapping of the resistances of all superconducting splices during the 2009 commissioning campaign. Since April 2010, when the LHC was successfully restarted at 3.5TeV, every bus bar interconnection is constantly monitored by the nQPS electronics. The acquired data are saved to the LHC Logging Database. The paper will briefly describe the data analysis method and will present the results from the two years of resistance measurements. Although no splice was found with resistance higher than 3.3nOhm and no significant degradation in time was observed so far, the monitoring of splices will stay active till the end of LHC 3.5TeV run. The detected outliers will be repaired during the Splice Consolidation Campaign in 2013-2014.  
THPPD031 Measurement of the Residual Resistivity Ratio of the Bus Bars Copper Stabilizer of the 13 kA Circuits of the LHC 3572
  • A. Apollonio, S.D. Claudet, M. Koratzinos, R. Schmidt, A.P. Siemko, M. Solfaroli Camillocci, J. Steckert, H. Thiesen, A.P. Verweij
    CERN, Geneva, Switzerland
  After the incident of September 2008, the operational beam energy of the LHC has been set to 3.5 TeV, since not all joints of the superconducting busbars between magnets have the required quality for 7 TeV operation. This choice is based on simulations to determine the safe current in the main dipole and quadrupole magnets, reproducing the thermal behavior of a quenched superconducting joint by taking into account all relevant factors that affect a possible thermal runaway. One important parameter of the simulation is the RRR (Residual Resistivity Ratio) of the copper stabilizer of the busbar connecting superconducting magnets. A dedicated campaign to measure this quantity for the main 13kA circuits of the LHC on all sectors was performed during the Christmas stop in December 2010 and January 2011. The measurement method as well as the data analysis and results are presented in this paper.  
THPPR036 Quench Limit Calculations for Steady State Heat Deposits in LHC Inner Triplet Magnets 4050
  • D. Bocian
    IFJ-PAN, Kraków, Poland
  • F. Cerutti, B. Dehning, A.P. Siemko
    CERN, Geneva, Switzerland
  In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. A Network Model is used to simulate the thermodynamic behavior of the superconducting magnets. In previous papers the validations of network model with measurements performed in the CERN and Fermilab magnet test facilities were presented. This model was subsequently used for thermal analysis of the current LHC inner triplet quadrupole magnets for beam energy of 3.5 TeV and 7 TeV. The detailed study of helium cooling channels efficiency for energy deposits simulated with FLUKA is presented. Some conclusions are drawn on expected inner triplet magnets quench limit.  
THPPR040 First Operational Experience with the LHC Machine Protection System when Operating with Beam Energies Beyond the 100 MJ Range 4062
  • M. Zerlauth, R.W. Assmann, B. Dehning, M. Ferro-Luzzi, B. Goddard, M. Lamont, R. Schmidt, A.P. Siemko, J.A. Uythoven, J. Wenninger
    CERN, Geneva, Switzerland
  The LHC made a remarkable progress in luminosity production during 2011 operation. This was made possible by a progressive increase of beam intensities by more than 5 orders of magnitude, reaching stored beam energies beyond 100MJ at the end of the year. The correct functioning of the machine protection systems was vital during initial operation and even more when approaching nominal beam parameters, where an uncontrolled loss of a small fraction of the beam is already sufficient to damage accelerator equipment or the large experimental detectors The machine protection system depends on the interplay of many different elements: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers, etc. The strategy applied during 2011 to allow for an efficient but yet safe increase of the beam intensities is presented along with the associated risks and drawbacks of a too aggressive approach. The experience gained with the key systems will be discussed along with possibilities to further enhance machine availability whilst maintaining the current level of safety.