Comparative analysis of design options for current leads for Wendelstein 7-X magnet system

The Wendelstein 7-X Project at Max Plank Institute for Plasma Physics, Germany, has a need of analytical and engineering design study for forced flow cooled 18 kA current leads. The main criteria for the current leads' design should be reliability, serviceability, investment and total operating costs. Since the magnet duty cycle has very long idle current periods, two options look worth considering: gas-cooled conventional, current leads properly optimized for the duty cycle to operate in over-current mode (so-called. overloaded leads), and binary current leads with high temperature superconducting part. The options are analyzed in detail and optimized to minimize total operating cost with holding the serviceability in emergency case.