Examination of contacts between strands by electrical measurement and topographical analysis

The contact resistance between crossing strands of Rutherford type superconducting cables has been proven to be an essential parameter for the behaviour of the main magnets in accelerators like the LHC. A strong development program to study the parameters fixing its value has been launched at CERN. The electrical contact resistance of individual strands with pre-selected coatings has been studied at 4.2 K under varying loading force by means of a 3 contacts DC method. The electro-mechanical properties of contacts have been studied on bare strands and strands with Sn, or Ni, or Zn based coatings, The contact resistances measured on strands were compared to measurements made on cables. Contact resistance properties were analysed with respect to the requirements for the LHC main magnet cables.