27 August 2017 to 1 September 2017
RAI Congress Center, Amsterdam, The Netherlands
Europe/Amsterdam timezone

Current transport characteristics of a superconducting joint between REBCO conductors made by a novel method

28 Aug 2017, 13:15
1h 45m
Posters Area

Posters Area

Poster Presentation of 1h45m F6 - Joints between Superconductors Mon-Af-Po1.09

Speaker

Yoshinori Yanagisawa (RIKEN)

Description

The superconducting joint technology used for high-temperature superconductors (HTS) is key for realizing persistent operation of HTS magnets. Recently we have succeeded in developing a superconducting joint between REBCO conductors using a polycrystalline intermediate, which has a critical current (Ic) of >100 A at 77 K [1]; A REBCO micro-polycrystalline intermediate was prepared on the surface of the REBCO layer of a conductor and it was transformed into large poly-crystals or single-like crystals as a joint.
We measured the persistent field decay of a small double pancake coil, terminated with this type of joint, at 77 K in a self-field with an operating current of ~10 A (~14% of the calculated coil Ic) for three days. The field decay rate decreased exponentially for the first several hours and then logarithmically, corresponding to a characteristic resistance between ~3×10^-12 to ~5×10^-13 Ω. The logarithmic decay implies that the joint resistance was not constant and might depend on flux creep. The effect of screening current relaxation on field decay and the coil load factor dependence will be investigated.
We also measured Ic-B characteristics of the joint in the temperature range from 4 K to 77 K in a field of <10 T. In a self-field, Ic at 4 K was ~7 times higher than that at 77 K. At 4 K, Ic steeply reduced with the field of <1 T and gradually decreased in the range of 1-10 T. The result shows that the joint structure includes a superconducting current path which is weak against a magnetic field. The superconducting current mechanism through the joint device will be discussed based on SEM and TEM observations.
[1] T. Nagaishi et al., Presented at 1st Asian ICMC and CSSJ 50th Anniversary Conference, 3A-p02, Kanazawa, Nov.7-10(2016)
This work is supported in part by the MEXT.

Submitters Country Japan

Primary authors

Yoshinori Yanagisawa (RIKEN) Takeshi Ueno (Sophia University) Mr Kazama Yamagishi (Sophia University) Tomoaki Takao (Sophia University) Mr Kotaro Ohki (Sumitomo Electric Industries, Ltd.) Mr Takashi Yamaguchi (Sumitomo Electric Industries, Ltd.) Dr Tatsuoki Nagaishi (Sumitomo Electric Industries, Ltd.) Dr Hitoshi Kitaguchi (National Institute for Materials Science) Takeharu Kato (Japan Fine Ceramics Center) Daisaku Yokoe (Japan Fine Ceramics Center) Tsukasa Hirayama (Japan Fine Ceramics Center) Yuichi Ikuhara (The University of Tokyo) Dr Renzhong Piao (RIKEN) Dr Hideaki Maeda (RIKEN)

Presentation Materials