  We have developed a model that describes the transverse load degradation in
Nb3Sn CICCs, based on strand and cable properties, and that predicts how such
degradation can be prevented. We present the model for Transverse
Electro-Magnetic Load Optimisation (TEMLOP) and report the first results of
computations for ITER type of conductors, based on the measured properties of
the internal tin strand used for the Toroidal Field Model Coil (TFMC). The most
important conclusion of the model computations is that the problem of the
severe degradation of large CICCs can be drastically and straightforwardly
solved by increasing the pitch length of subsequent cabling stages. It is for
the first time that an increase of the pitches is proposed and no experimental
data are available to confirm this outcome of the TEMLOP model. Larger pitch
lengths will result in a more homogeneous distribution of the stresses and
strains in the cable by significantly moderating the local peak stresses
associated with the intermediate-length twist pitches. The twist pitch scheme
of the present conductor layout turns out to be unfortunately close to a worst
case scenario. It is possible to improve the ITER conductor design or the
operation margin, by mainly a change in the cabling scheme. We also find that a
lower cable void fraction and larger strand stiffness add to a further
improvement of the conductor performance.
