Studies to clarify methods to reduce AC losses of high temperature superconducting (LHS) wires

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In this project we performed the following studies to clarify methods to reduce AC losses of high temperature superconducting (LHS) wires.1) Measurement of AC losses of HTS wires in DC and AC external magnetic field.We developed a method to measure AC transport current losses of superconducting wires in the external magnetic field avoiding spurious losses. Using this method, we measured the AC etransport current losses of various HTS wires, such as Bi 2223 silver sheathed tapes, YBCO tapes and Bi22l2 rod. As the results, we found that in many case there were significant discrepancies between the measured data and values calculated from Norris formula which was widely accepted. to well agree with measurement. We also measured the transport current AC loss of a wire in assembled, conductor and found that the AC loss was decreased due to the magnetic field produced by transport currents of wires adjacent to the wire whose loss was measured. This result suggests that the transport current loss can be reduced by proper design of wire structure.2)Modeling the electromagnetic behavior of LTS wire to calculated the AC loss.We made a theoretical model to quantitatively calculate the AC losses of HIS wires by modifying the theoretical model developed for the low temperature superconductor (LTS). The theoretical model for HTS wires was verified by the result of the study 1).3)Proposing methods to design a wire with low AC losses.Based on the theoretical model formulated by the study 2), we proposed methods to reduce the AC losses. Validity of the methods were demonstrated by using LTS wires and assembled conductor simulating a wire with low loss structure.By above studies, we consider the purpose of the project was well fulfilled.