RESULTS_OF_ROUND_ROBIN_TEST_OF_RESIDUAL_RESISTANCE_RATIO___________________________________________________________

                                 IN_Cu/Nb-Ti_COMPOSITE_SUPERCONDUCTOR________________________________________



                  T._Matsushita1________, E. S. Otabe1 , S. Murase2 , K. Osamura3  and C. Y. Hua4

                1) Kyushu Institute of Technology, 680-4 Kawazu, Iizuka 820-8502, Japan

        2) Toshiba Corporation, 4-1 Ukishima-cho, Kawasaki-ku, Kawasaki, 210-0862, Japan

                3) Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan

                          4) Beijing General Research Institute for Non-ferrous Metals,

                               2 Xin Jie Kou Wai Dajie, Beijing 100088, P. R. China



    A  round  robin  test  was  carried  out  on  the  residual  resistance  ratio  (RRR)  of  a  Cu/Nb-Ti

composite superconductor based on the fourth working draft of Working Group 4 in IEC/TC90.

13 institutes from 5 countries joined the test and the number of the obtained data was 77.  The

diameter of the specimen was 0.86 mm including an insulating layer and the Cu/Nb-Ti ratio was

6.5.  The number of superconducting filaments was 16 and their diameter was about 70 m.  The

effect of bending strain of the specimen on RRR was corrected using an empirical formula on the

enhancement of resistivity of a pure copper at low temperatures.  The mean value, the standard

deviation  and  the  coefficient  of  variation  (COV)  were  178.5,  4.4  and  2.44  %,  respectively.  This

result  shows  that  the  present  measuring  method  described  in  the  fourth  working  draft  can  be

adopted  as  a  standard.  The  details  of  the  effects  of  the  bending  strain  and  the  temperature  at

the measurement will be argued.