Speaker
Description
In recent years, High-Temperature Superconductors (HTS) have gained prominence in high-field applications, not only due to their elevated critical temperature (Tc) but also owing to their superior critical magnetic field (Bc2) at lower temperatures, surpassing 100 T and outperforming conventional superconductors in this regard. Recent advancements in practical conductor development based on HTS, specifically Rare Earth Barium Copper Oxide (REBCO) Coated Conductors (CCs), have opened avenues for superconducting solenoids capable of generating fields in the 30 T range. Among potential applications for such high fields, Nuclear Magnetic Resonance (NMR) spectroscopy stands out, as its resolution power for unraveling complex molecular structures increases proportionally with the intensity of the magnetic field. Two critical considerations are integral to the advancement of NMR systems based on REBCO ultra-high field magnets. Firstly, the magnet must operate in persistent current mode, wherein the current flows seamlessly within a closed superconducting loop. Secondly, a limitation arises as the available lengths of REBCO coated conductors are confined to unit lengths ranging from 100 to 200 m. These conditions necessitate the development of superconducting joints, with resistance in the order of R<10-12 Ω, between Coated Conductors. This task is notably challenging for REBCO due to its ceramic nature and the need for precise oxygen doping to achieve optimal functionality. Establishing a superconducting joint between two exposed surfaces of REBCO requires the simultaneous application of temperature and pressure. However, the inherent mechanical fragility of CCs, coupled with the challenges posed by the deoxygenation and potential decomposition of REBCO at elevated temperatures, presents a potential obstacle. Notably, the consequences of concurrently applying temperature and pressure remain largely unexplored in the literature. This study addresses this gap, undertaking a comprehensive analysis of the influence of these thermomechanical loads on the critical current (Ic) of commercial CCs. A variety of pressure and temperature combinations were systematically applied to the samples, and their critical current was measured at 77K, within a self-field. The insights gained from this research are pivotal for the advancement of a robust technology aimed at achieving superconducting joints in REBCO Coated Conductors.
