Stability analysis of the LHC main dipole and quadrupole magnets

by Marco Massimini

Tuesday 26 Feb 2013, 11:00 → 12:00 Europe/Zurich

30/7-010 (CERN)

Beam induced heat depositions can provoke quenches of the LHC superconducting magnets, particularly when the accelerator will run at full energy. In order to detect imminent quenches that would be detrimental for the operation, Beam Loss Monitors (BLM) were installed around the machine. The BLM efficiency requires a thorough knowledge of the maximum heat deposition the magnets can withstand without quenching, the so-called stability margin. We have developed 0-D and 1-D electric, thermal and hydraulic numerical models to simulate the superconducting cables behavior following an energy pulse. The heat transfer mechanisms occurring inside the conductor as well as towards the cooling helium bath are described depending on the different coolant phases, based on the existing experimental results. We present stability maps of the different LHC main dipoles and quadrupoles. The dependence of the stability margin on the transport current and on the magnetic field in the coil cross-section is analyzed, from beam injection to nominal operating conditions. A wide perturbation spectrum is considered, assuming heat deposition times from the micro-second time scale to steady-state conditions and heated lengths ranging between few millimeters and meters of cable.