Stochastic Analysis on the Factors Affecting Critical Current and Index Value of Multi-Tape Co-Wound NI HTS Coil

The estimation of critical current ($I_{\rm{c}}$) and the index value for single-tape wound coils and magnets is relatively straightforward. However, for multi-tape co-wound coils, the process becomes complex due to various factors influencing current distribution within the coil. This study conducts a numerical analysis to explore these factors and their impact on the$I_{\rm{c}}$and index value of multi-tape co-wound HTS coils. An equivalent circuit model, the multi-tape turn distributed circuit, is utilized to represent each tape turn in the coil. Key parameters such as the 77K self-field$I_{\rm{c}}$of REBCO (Rare Earth Barium Copper Oxide) tape, its index value, contact resistance, and lead resistance are treated as variables during the charging simulation. A stochastic approach is employed to analyze the relationship between these parameters and the coil's$I_{\rm{c}}$and index value through multiple simulations using randomly generated parameter values. The results demonstrate a strong correlation between the coil$I_{\rm{c}}$and the average$I_{\rm{c}}$of the REBCO tapes. Furthermore, the coil index value is found to be significantly influenced by the average contact resistivity between the REBCO tapes, and both the coil parameters are irrelevant to the tape lead resistance.