Abstract
Qualification tests of the ITER toroidal field (TF) conductor joints have been carried out by testing joint samples with test facilities in the National Institute for Fusion Science, NINS, Toki, Japan. The joint sample consists of two short TF conductors with the length of 1535 mm, which is restricted by the test facility with 9-T split coils and 100-kA current leads. The sample current is supplied from a dc 75-kA power supply. Each conductor has two joint boxes at both terminals. The lower joint is a testing part that is a full-size joint of the TF coil. The joint resistance of the lower joint is estimated from the increase of the average voltage drop among the six taps on the conductor against the currents. Five joint samples were tested until 2016, and all the samples satisfied the requirement of the joint resistance at less than 3 nΩ. The method of the measurement and the results are summarized, and the voltage distribution among the voltage taps is discussed.
Highlights
ACH Toroidal Field (TF) coil of ITER contains seven double-pancakes that are electrically connected each other with "twin-box" joints [1]–[4]
The joint sample consists of two short TF conductors with the length of 1,535 mm, which is restricted by the conductor test facility with the
While the 9 T split coils of the test facility are cooled with liquid helium, the CIC conductor sample is cooled with supercritical helium (SHe)
Summary
ACH Toroidal Field (TF) coil of ITER contains seven double-pancakes that are electrically connected each other with "twin-box" joints [1]–[4]. The twin-box joint is adopted for the TF coil terminal. The twin-box joint was firstly developed at CEA Cadarache (France) for Cable-In-Conduit (CIC) conductors [5]. Is attained by the direct contact of the superconducting strands pressed to the copper sleeve of the box and by soldering of adjacent copper sleeve of the two boxes [6], [7]. The required joint resistance of the ITER-TF conductor joints is less than 3 n! Takahata are with the National Institute for Fusion Science, NINS. Research and Development Directorate, National Institute for Quantum and Radiological Science and Technology, Naka, Ibaraki 311-0193, Japan
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