PPPL-4860
FEMCAM Analysis of SULTAN Test Results for ITER Nb3SN Cable-conduit Conductors
Authors: Yuhu Zhai, Pierluigi Bruzzone, Ciro Calzolaio
Abstract:
Performance degradation due to filament fracture of Nb3 Sn
cable-in-conduit conductors (CICCs) is a critical issue in
large-scale magnet designs such as ITER which is currently
being constructed in the South of France. The critical current
observed in most SULTAN TF CICC samples is significantly
lower than expected and the voltage-current characteristic is
seen to have a much broader transition from a single strand to
the CICC. Moreover, most conductors exhibit the irreversible
degradation due to filament fracture and strain relaxation
under electromagnetic cyclic loading. With recent success in
monitoring thermal strain distribution and its evolution under
the electromagnetic cyclic loading from in situ measurement
of critical temperature, we apply FEMCAM which includes
strand filament breakage and local current sharing effects to
SULTAN tested CICCs to study Nb3 Sn strain sensitivity and
irreversible performance degradation. FEMCAM combines
the thermal bending effect during cool down and the EM
bending effect due to locally accumulating Lorentz force
during magnet operation. It also includes strand filament
fracture and related local current sharing for the calculation
of cable n value. In this paper, we model continuous
performance degradation under EM cyclic loading based on
strain relaxation and the transition broadening upon cyclic
loading to the extreme cases seen in SULTAN test data to
better quantify conductor performance degradation.
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Presented at: 7th Mechanical and Electromagnetic Effects in Superconductors (MEM13) workshop, hosted by ITER in Aix-em-provence, France (Mar 12-13, 2013) Submitted to: Superconductor Science and Technology (March 2013)
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Download PPPL-4860 (pdf 991 KB pp)
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