Construction of the new prototype of main quadrupole cold masses for the arc short straight sections of LHC

Each cold mass of the short straight sections in the eight LHC arcs will co ntain a 3.25 m long twin aperture quadrupole of a nominal gradient of 223 T /m. This magnet will be aligned in a 5.3 m long inertia tube together with auxiliary magnets on each end. On the quadrupole connection end either a pa ir of 38 cm long octupole or trim quadrupole magnets will be mounted, on th e other end there will be combined sextupole-dipole correctors with a yoke length of 1.26 m. The powering of the main quadrupoles will be assured by t wo pairs of copper stabilized superconducting bus-bars placed inside the co ld mass next to the bus-bars for the main dipole magnets. Each of the two q uadrupole apertures will be connected to its quench protection diode.he con struction of three prototypes has been entrusted to the CEA/Saclay laborato ry, in the frame of the special French contribution to the LRC project. The first cold mass prototype has been completed and warm-measured for its mul tipole content at CEA. The second cold mass is presently under completion. The paper will review the experience with the development of the quadrupole coils and cold mass construction and gives the results of the first warm m agnetic measurements. An outlook for the series manufacture of the 400 are quadrupole magnets and their cold masses for the LHC machine will complete the report.