Novel 2G HTS Multifilamentary Conductor Design for AC Applications

Abstract

2G HTS wires need substantial development to allow ac applications with acceptable losses in ac magnetic fields perpendicular to the tape plane. Filament transposition is necessary to avoid large coupling currents and also to insure a uniform current flow through all the filaments, both of which are essential to minimize ac losses. Conductor twisting solves only the first part of the problem and is not really practical in a tape-shaped wire needing to be wound for instance into compact coils of various shapes. We set out to evaluate a new two-dimensional transposition approach for striated, multifilamentary 2G HTS wire. The new concept uses a so-called transposition zone, located along a linearly striated conductor. In this 7-10 cm long zone all filaments are transposed. The repeat distance of this transposition zone can be as short as 10 m or as long as 100 m, depending on the particular superconducting device and the anticipated ac magnetic fields. In this project a successful transposition approach with acceptable losses was developed. Both the striation method using lateral translations, and sound junction types using different materials, were demonstrated.Index Terms-AC loss, filament transposition, high temperature superconductors, YBa 2 Cu 3 O 7 x .

Self-field quench behaviour of YBa2Cu3O7−δcoated conductors with different stabilizers

“…The densities of the materials at room temperature are used. It is found that the Cu layer in the conductor has a RRR ∼35 [24]. Thus when using the properties from Cryocomp, Cu with RRR = 35 in zero magnetic field is set.…”

“…Thus, the substrate acts as a stabilizer during the quench. It is actually the case for the SS-SS sample, as the resistivity of the NiW substrate is lower than that of SS (table A.1 and [24]). Recent effort shows the possibility of having Cu substrates for YBCO coated conductors [25,26].…”

Ink-jet printing of YBa2Cu3O7superconducting coatings and patterns from aqueous solutions

“…For AC applications of coated conductors, high conductivity or superconducting regions between the filaments would increase coupling losses. 26,27 By using multiple depositions, without an interim thermal treatment, the coffee-ring effect is strongly reduced due to an increased amount of deposited material.…”

“…Ideally, the filaments should also be transposed regularly along the conductor. 25,27 The ability to over-print multiple layers with any chosen pattern at high resolution could allow this to be achieved much more costeffectively by ink-jet printing than conventional mechanical methods. 27 Previous reports mention the use of inkjet printing for the deposition of buffer layer structures using organic solvents, while for YBCO there have been very few reports of ink-jet printing.…”

“…25,27 The ability to over-print multiple layers with any chosen pattern at high resolution could allow this to be achieved much more costeffectively by ink-jet printing than conventional mechanical methods. 27 Previous reports mention the use of inkjet printing for the deposition of buffer layer structures using organic solvents, while for YBCO there have been very few reports of ink-jet printing. 19,[28][29][30][31] Here, the successful production of YBCO coatings and multi-filamentary patterns from aqueous inks is extensively described for the first time.…”