Influence of the Surface Layer on YBaCuO Coated Conductors Quench Processes

The study of the thermal stability process in second-generation (2G) high-temperature superconductors is important to determine its optimal performance in applications. When a fault takes place during operation, the heat generated must be evacuated as fast as possible in order to protect the superconductor from damage. If conductors are immersed in liquid nitrogen (LN), thermal stability is strongly dependent on the tape orientation, proximity between tapes, and the characteristics of the surface, such as roughness, presence of insulating materials covering the conductor, etc., which will influence the recovery time of the conductor after a fault. In this contribution, we analyze quench and cooling processes of 2G conductors subjected to over-currents and immersed in LN. The sample surface has been modified in order to induce different roughnesses. The observed behavior has also been compared with that of samples covered with polyimide (kapton) or varnish. Information about recovery times for the different LN cooling regimes has been obtained.