In the framework of the development of an experimental 10 T Nb3Sn dipole coil for the LHC at CERN the effects of transverse stress on Rutherford type of Nb3Sn cables have been investigated. For this purpose a special facility was designed and taken into operation in which the voltage-current behaviour of short pieces of Nb3Sn cables can be investigated in a background field up to 11 T and an applied stress of 300 MPa. The repulsive Lorentz force of 250 kN, generated by a set of superconduct9g coils, is used to impress the cable over an area of 20x42 mm maximum, in presence of a transport current up to 40 kA. In this paper the testing equipment is described and the fiist results of the observed critical current degradation of two Nb3Sn cables are discussed. It was found, that current reduction starts immediately upon loading and that already at transverse compressive stress of 100 MPa the critical current at 11 T is reduced by more than 20 % for one cable and even about 60 % for the other one. Furthermore, it seems, that the edges of the Rutherford type of cable are much more sensitive to the applied force than the cross-over points of the strands.

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Measurement of voltage-current characteristics in multifilamentary wires, showing the transition from the superconducting to normal state, provides information about the quality of the wires and their production techniques. In this paper several methods of describing this transition are discussed. In general, the so-called n-power law turns out to be adequate in the critical current region. The dependence of n on the magnetic field yields information about the inner structure of the wire, especially whether the limitation of the current is caused by intrinsic or extrinsic effects. However, when submicrovolt measurements are carried out on short-sample specimens with high-resistivity matrices, in several ranges of current other n-values can be distinguished. This can be caused by a current diffusion process. A different way of describing the resistive transition is by means of a critical current distribution function. Such a function can be found by calculating the second derivative of the voltage with respect to the current.

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