Summary of NbTi Strand Performance for ITER PF Conductors in China

Abstract

China, who was in charge of most of the poloidal field (PF) conductor unit lengths manufacturing for the ITER Project, has supplied all the required PF conductors and finished the PF package successfully. Around 130 t of NbTi strands were supplied and used for the PF conductors. During the package execution process, the Chinese Domestic Agency (CNDA) has organized the verification for the NbTi strand acceptance tests based on the requirements of the ITER procurement arrangement (PA). The verification tasks for NbTi strands were undertaken by the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP). In total, about 550 billets of NbTi strands have been verified and supplied for the PF conductors. The verification levels fit the ITER PA requirements. The test results showed that the quality of the NbTi strands has been well controlled. In addition, in order to supply essential data for the conductor performance prediction and analysis, a full critical current I c characterization of the NbTi strands, which requires a measurement of I c versus field, B and temperature, T, has been obtained using the test facilities from the National Institute of Standards and Technology (NIST) and ASIPP. The parameterization using the Bottura scaling law for the strand with I c close to the average value from the verification results has been analyzed. The test methods and strand performances are reviewed and summarized in this article.