SIMULATION AND OPERATIONAL EXPERIENCE WITH ENERGY EXTRACTION IN THE LHC SUPERCONDUCTING MAGNET CHAINS

The quench protection scheme for the superconducting main magnet chains of the LHC particle accelerator, which is presently being commissioned at CERN, comprises DC cur-rent discharges in power circuits with an inductance of up to 15.7 H and currents up to 13 kA. The electrical arc, with emphasis to its extinction, has been modeled for the specially designed electro-mechanical opening switches used for the extraction of the 1.3 GJ of stored energy in each of the eight sectors of the machine. The model allows the analysis of the various phases of the opening process. The paper presents the boundary conditions, the basic parameters and the limitations of the model, then provides the first results from the recent powering and discharging of the dipole and quadrupole chains during the on-going hardware commissioning of the machine. We describe in particular features related to the arc behavior in arrays of series- and parallel connected switches, such as used for extraction in the LHC main magnet chains.