Growth Rate and Morphology of Nb3Sn Layers in ITER-Type Bronze-Processed Wires Under Different Diffusion Annealing Regimes
The Nb3Sn-based bronze-processed multifilamentary composites have been fabricated at the Bochvar Institute of Inorganic Materials, Moscow, Russia, and studied by electron microscopy to determine the relationships between their structural parameters and annealing duration at different temperatures (575 °C, 650 °C, 750 °C). The structure of superconducting layers during their formation is characterized by thickness, average size of equiaxed grains, and by the fraction ratio of columnar and equiaxed grains. It was found that at high diffusion annealing temperatures (above 650 °C), the superconducting layers grow much faster, but the average size of equiaxed Nb3Sn grains even under a short exposure (10 h) is much larger than after a long low-temperature annealing. It is shown that to ensure the best current-carrying capacity of Nb3Sn-based wires in high magnetic fields, it is necessary to take into account different trends: on the one hand, the possibility of approaching the Nb3Sn phase stoichiometry and providing its maximum amount and on the other hand to avoid the undesirable growth of grains resulting in a lower pinning force.
Russia's Contribution to the ITER TF Magnets
The ITER toroidal field (TF) magnet system consists of 18 D-shaped coils, each of which is formed by five regular double pancakes (rDP) and two side double pancakes (sDP). Manufacturing of conductors for the TF coils, which are Nb3Sn-based cable-in-conduit conductors, has been shared among six ITER Domestic Agencies, including the Russian Federation (RF). The RF share includes manufacturing of eighteen 760-m conductors for rDP and eight 415-m conductors for sDP, i.e., almost 4 out of 18 TF coils will be produced from the conductors supplied by RF. In order to fulfil project obligations, facilities for Nb3Sn strand, cable, and conductor production had been established, and after successful qualifications, the manufacturing phase began. The manufacturing activities went on for six years, starting with the first strand production in 2009 and finishing with a successful wrap-up of conductor manufacturing and delivery in 2015. In this paper, highlights of the TF conductor production from the superconducting strand manufacturing up to the results of conductor full-size sample tests in the SULTAN facility are presented.
Garnitures mécaniques d'étanchéité
Keywords: etancheite ; mecanique Reference Record created on 2005-11-18, modified on 2016-08-08