Critical current of prototype conductors for LHC dipole magnets

Electrical measurements on conductors developed for Large Hadron Collider (LHC) dipole magnets are reported. Two kinds of measurements were carried out: critical current on the prototype cables and AC magnetic measurements on the strands. To perform critical current measurements the samples were placed in the bore of the superconducting magnet MARISA, which allows measurements up to 6.5 T while temperature ranges from 1.8 to 5 K. The current is supplied using an inductive method: the background magnet is the primary winding of a transformer having the sample as a secondary winding. The current is measured by Hall probes placed near the samples; the critical current is measured by the resistive criterion rho =10/sup -14/ Omega m. Critical currents up to 60 kA were measured for four different samples. AC magnetic measurements, like AC susceptibility and penetrated and trapped magnetic flux, were carried out in order to study the connections between the critical current and the effective critical field. Information about the filament coupling at low field is also obtained.