Strand coating for the superconducting cables of the LHC main magnets

The electrical resistance of contacts between strands in the Rutherford typ e superconducting cables has a major effect on the eddy current loss in cab les, and on the dynamic magnetic field error in the LHC main magnets. In or der to guarantee the value and constancy of the contact resistance, various metallic coatings were studied from the electrical and mechanical points o f view in the past, We report on the molten bath Sn95wt.Ag5wt. coating, oxidized thermally in a ir after the cabling is completed, that we adopted for the cables of the LH C main magnets. The value of the contact resistance is determined by the st rand coating and cabling procedures, oxidation heat treatment, and the magn et coil curing and handling, Chemical analysis helps to understand the evol ution of the contacts. We also mention results on two electrolytic coatings resulting in higher co ntact resistance.