Energy extraction in the CERN large hadron collider (LHC)

Summary form given only, as follows. In case of a resistive transition (a quench) fast and reliable extraction of the magnetic energy, stored in the superconducting coils of the electromagnets of a particle collider, represents a vital part of its magnet protection system. Together with the quench detectors, the quench heaters and the presence of cold by-pass diodes across each magnet the energy extraction facilities provide the requisite means of protecting the quenching superconductors from damage due to excessive local energy dissipation. In the case of the LHC machine at CERN, the energy, stored in each of its eight superconducting dipole chains, exceeds 1.3 GJ. This energy will be absorbed in huge dump resistors, located in the underground collider tunnel or adjacent galleries, during the exponential decay of the 13 kA magnet excitation current, as a result of the activation of the dump switches. Also the sixteen, 13 kA quadrupole chains and some two hundred, 600 A circuits of LHC corrector magnets will be equipped with extraction systems. The extraction switch-gear is based on specially designed, mechanical DC breakers, combined with capacitive snubber circuits for arc suppression. The paper contains a complete system description, including modelling and simulation of the pulsed powering of the dump switches. It presents the calculation, concept and design, the manufacture and results from type and reliability testing of the prototypes of the various components, including the control and acquisition electronics. Related security, redundancy and radiation issues will be highlighted. Finally, the plans for the installation and operation of the almost 300 tons of extraction equipment will be described.