Test Results on the Long Models and Full Scale Prototype of the Second Generation LHC Arc Dipoles

With the first 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 aperture, is wound with 15 mm wide cable arranged in a 5 coil blocks layout. The 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, and one 15 long dipole prototype, manufactured totally in Industry in the frame of a CERN-INFN collaboration for the LHC. After a brief description of particular features of the design and of the manufacture, test results are reported and compared with the expectation. One magnet reached the record field for long model dipoles of 9.8 T but results have not been well reproducible from magnet to magnet. Guidelines of the modifications that will appear in the next generation of long magnets, based on a six block coil design, are indicated in the conclusions.