Stability against transient disturbances in cable-in-conduit conductors cooled by supercritical helium

The stability of cable-in-conduit superconductor (CICC) is analyzed for transient disturbances applied to a strand. The study is focused on the effects of thermal contact between strands and transient heat transfer in supercritical helium, including thermal expansion to neighboring voids. The process of normal zone growth from strand to strand was numerically modeled using a 2-D approximation. Stability margins were determined for the well cooled and poorly cooled regimes. Interstrand contacts as well as longitudinal helium flow involve more strands and helium voids, thus significantly improving CICC stability. The effect of helium thermal expansion, transient heat conduction and shape of disturbance is discussed.<>