On the Stability Analysis of HTS Conductors for Fusion Magnet Design

As extended to the fusion magnet design, potential need of HTS conductor has been highlighted even in the large-scale applications on the strength of their outstanding thermal stability. As much as practical guidance of such a design must take care of the inherent properties of HTS conductors in their operating conditions, a few recent approaches have focused on the distinctive quench behavior of HTS conductors in contrast to the LTS-based design. However, the prevalent idea has been established with a lack of foundation on the quench condition, and may result in conceptual misleading about the design criteria. In this work, we reevaluate the previous design study based on the transient thermal-hydraulic modeling using the THEA code, which has been referred as a new idea of stability criterion to be relevant to the peculiar aspect of the HTS-based CICCs (Cable-In-Conduit Conductors) as supported by their results of numerical model. Through the investigations to the underlying physical conditions, we show that the simple steady-state heat balance in uncooled condition can be used to estimate the runaway temperature, which is particularly sensitive to the initial length of normal zone under the simple 1-d thermal problem of nonlinear solid composite. As a result, some practical gains are discussed on the design assessment with general comments to the thermal hydraulic model to evaluate the stability condition and the tolerance of quench detection.