Design of a multipurpose test facility (MTF) for HTS cables

Abstract The High Field Magnet (HFM) program foresees, among others, the systematic measurement and assessment of mechanical, thermal, and electrical properties of high temperature superconductors (HTS) cables. These measurements are a key factor to characterize the conductor, verify its performance and control the production quality. These values are also necessary inputs to size the prototype magnets that will use HTS windings. Cable and coil properties must be measured at room temperature, in liquid nitrogen, in helium gas at 20 K – 30 K, and in liquid helium at about 5 K. Cable samples and small coils are tested at different temperatures, and under a given force or deformation. The mechanical and electrical loads can be applied simultaneously or in different combinations. The output data span over a large range of signals: strain measured by strain gauges, optical fibers, or digital correlation techniques, critical currents, displacements, and structural deformations. At the moment, any cable property can be measured individually. The proposed multipurpose test facility is a testing station capable of simultaneous measurements to facilitate the development of correlation laws: for example, by powering a small HTS coil at 20 K while measuring its deformation via digital image correlation; or measuring the critical current in a sample under a given mechanical pressure or after a certain amount of load cycles. Another important requirement is the flexibility and the short turnaround time to test samples. This note describes the multipurpose test facility designed at CERN and under construction. Some examples of possible measurements are given as well.