Electromagnetic behaviour and thermal stability of a conduction-cooled, no-insulated 2G-HTS coil at intermediate temperatures

• Published in: Cryogenics (Guildford) 2020-06, Vol.108, p.103070-9, Article 103070
• Main Authors: Cubero, A., Núñez-Chico, A.B., Navarro, R., Angurel, L.A., Martínez, E.
• Format: Article
• Language: English
• Subjects: Coil losses; Conduction cooling; Cryogenic equipment; Electromagnetic properties; Epoxy resins; High temperature superconductors; High vacuum; HTS no-insulation coils; Insulation; Pancake coils; Superconductor; Thermal conductivity; Thermal contact conductance; Thermal stability; Thermodynamic properties
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2020.103070

•Charge and discharge modelling of No-Insulated (NI) HTS coils from 5 K to 77 K.•Contribution of turn-to-turn and magnetization loss for variable current & ramp rates.•Good agreement between experimental and numerical critical currents (Ic) of the coil.•Good thermal stability of NI coils and current leads at high currents, reaching 400 A.•Thermal contact conductance between layers of conduction-cooled double pancake coil. The electromagnetic and thermal properties of a double pancake coil made of second generation high temperature superconductor, 2G-HTS, have been studied. The coil was wound with no-insulation between turns (NI coil) and was later impregnated with epoxy resin and glued to a copper support plate. The coil was thermally anchored to the cryocooler cold finger and cooled by conduction. After several thermal cycles no degradation of its superconducting properties was observed. The coil was operated under high vacuum and high currents (up to 400 A in steady conditions) at different temperatures in the range between 5 K and 77 K, with special focus on the analysis above 30 K. The charge and discharge characteristics, and the experimentally measured and numerically estimated critical currents, have been studied. The different loss contributions during current ramp and the thermal contact conductance between different parts of the double pancake coil have been measured. The implications of these two factors on the thermal stability and the behaviour of the whole cryogenic system are discussed.