Design of an Apparatus to Evaluate the Turn-to-Turn Thermal Conductivity of MI and NI HTS Coil

The Metal as Insulation and more generally the No-Insulation windings are promising for the protection of DC and slow ramping HTS magnets. The modeling of the thermal behavior during a quench in order to design the protection of a magnet is highly dependent on parameters set by materials and fabrication. The electrical resistance between turns has been widely studied worldwide, but the turn-to-turn thermal conductivity of MI windings stays relatively unknown. Turn-to-turn thermal conductivity may have a significant role in the dynamics of a quench and on the hot spot temperature. This motivated us to develop a specific apparatus for evaluating this turn-to-turn thermal conductivity. Because we are working with HTS dry stacks the thermal conductivity depends not only on temperature but also on radial pressure. This paper present the design of an apparatus to evaluate the thermal conductivity of an HTS stack under different radial compression and at different temperature. The measurements are made with an isoperibolic cell using the steady-state differential method. This article details the mechanical and thermal design and the fabrication steps of the first thermal samples. We also present the first results of thermal conductivity obtained at 20 MPa and 5.5 K, which is close to our theoretical prediction.