State of the LHC main magnets

The main features of the dipole magnet design have been frozen in 1996 and important steps for the preparation of their series production are being taken in the current year. To finalize the technical specifications of the superconducting cables and other components, a number of detail variants are being validated with the construction and test of short and long magnets. Thus, beside a number of 1 m long models, four 10 m long models of the main dipoles and two 14.2 m prototypes are being assembled in industry and at CERN. The fabrication of a further set of 3 full length dipoles is also starting in industry to verify the reproducibility of production and performance. The lifetime and fatigue test of the String Test Facility, consisting of three dipoles and one quadrupole and simulating the basic periodic cell of the LHC, has been successfully concluded. The String was repetitively cycled between the injection field of 0.6 T and the operational field of 8.4 T, 24 hours per day, and has accumulated more than 2100 cycles, corresponding to about ten years of machine operation. The final design of the main quadrupoles, based on the use of the dipole coil outer layer cable, is being worked out by CEA, Saclay and the construction of two new prototypes has been launched.