Thermal stability of superconducting magnet system in a tokamak Dr hab. inż. Leszek Malinowski, prof. PS Dr inż. Monika Lewandowska
TF coil conductor design PF coil conductor design
Thermal stability • Conductors made of pure superconducting material are thermally unstable • Cables constituted of the superconducting material embeded in the normal metal can operate stable.
Full stabilization q > Q where Imax- maximum stable operating current, R- normal state resistance, h- heat transfer coefficient, P- cooled perimeter, Tc- critical temperature, To- coolant temperature.
Main disadvantage of fully stable wires is large amount of stabilizer. This implies: • low overall current density of the conductor • large size and big cost of a superconducting device Modern superconducting wires are partly stable. It implies limited amount of energy which can be dissipated in a cable without disturbing its safe operation.
Critical energy E- energy of dissipation Ecr- critical energy of the conductor. Critical energy - the minimum energy of the thermal disturbance destroying the superconductivity
Mathematical model of normal zone Tn- temperature of the n thermal component Vh- volumetric flow in the h cooling channel ph- pressure in the h cooling channel Th-temperaturein the h cooling channel Ie-current in the econducting component
Main goals of studies and anticipated results • Identification and quantification of energy disturbances and heat sources in superconducting magnet system in a fusion reactor. • Analysis and modelling of heat transfer phenomena in cable-in-conduit-conductors (CICC) used in fusion reactor magnets. • Development of an analytical model of a normal zone in CICC. • Formulation of stability criteria for CICC. • Performance of sample calculations and validation of the results by comparison with experimental results.