Test results on the long models and full scale prototypes of the second generation LHC arc dipoles

With the test of the first full scale prototype in June-July 1998, the R&D on the long superconducting dipoles based on the LHC design of 1993-95 has come to an end, This second generation of long magnets has a 56 mm coil ape rture, is wound with 15 mm wide cable arranged in a 5 coil block layout. Th e series includes four 10 m long model dipoles, whose coil have been wound and collared in industry and the cold mass assembled and cryostated at CERN , as well as one 15 m long dipole prototype, manufactured totally in indust ry in the framework of a CERN-INFN collaboration for the LHC, After a brief description of particular features of the design and of the manufacturing, test results are reported and compared with the expectations. One magnet r eached the record field for long model dipoles of 9.8 T but results have no t been well reproducible from magnet to magnet, Guidelines for modification s that will appear in the next generation of long magnets, based on a six b lock coil design, are indicated in the conclusions.