Forced flow He vapor cooled critical current testing facility for measurements of superconductors in a wide temperature and magnetic field range

As superconducting materials find their way into applications, there is increasing need to verify their performance at operating conditions. Testing of critical current with respect to temperature and magnetic field is of particular importance. However, testing facilities covering a range of temperatures and magnetic fields can be costly, especially when considering the cooling power required in the cryogenic system in the temperature range below 65 K (inaccessible for LN2). Critical currents in excess of 500 A are common for commercial samples, making the testing of such samples difficult in setups cooled via a cryocooler, moreover it often does not represent the actual cooling conditions that the sample will experience in service. This work reports the design and operation of a low-cost critical current testing facility, capable of testing samples in a temperature range of 10-65 K, with magnetic field up to 1.6 T and measuring critical currents up to 900 A with variable cooling power. (C) 2016 The Authors. Published by Elsevier Ltd

Uniform trapped fields produced by stacks of HTS coated conductor tape

The trapped magnetic field profile of stacks of GdBa2Cu3O7-x superconducting tape was investigated. Angled stacks of superconducting tape were magnetized and found to produce very uniform trapped field profiles. The angled stacks were made of 12 mm x 24 mm solder coated tape pieces and were bonded together following a brief consolidation heat treatment. Layering multiple stacks together and adding a ferromagnetic plate beneath the samples were both found to enhance the magnitude and uniformity of the trapped field profiles. Stationary and time-dependent critical state finite element models were also developed to complement the experimental results and investigate the magnetization process. The size and shapes possible with the angled stacks make them attractive for applications requiring uniform magnetic fields over larger areas than can be achieved with existing bulk rings or tape annuli

Spark-discharge plasma as a method to produce low AC loss multifilamentary (RE)Ba2Cu3O7 coated conductors

If coated conductors are to be used in large-scale ac applications such as motors and generators, energy losses must be minimised. Hysteretic ac losses can be reduced by dividing the coated conductor into filaments. In this study, a new method for producing filamentary coated conductors is presented. An electrical spark discharge was used to selectively degrade regions of superconducting tape. The robust, noncontact and scalable method was used to striate tapes into four filaments. The filamentary samples had lower ac losses than nonstriated tapes with less than a 7% reduction in current carrying capacity

Low AC loss inkjet-printed multifilamentary YBCO coated conductors

Impressive performance has been achieved in (RE)Ba2Cu3O7-delta (REBCO) coated conductors, but for many applications, the high cost and ac losses remain prohibitive. Inkjet printing methods combine scalability and low equipment cost with high-resolution patterning, potentially addressing both issues by enabling the production of multifilamentary coated conductors without subtractive processing. The successful production of multifilamentary superconducting YBa2Cu3O7-delta (YBCO) structures by inkjet printing of a low-fluorine YBCO precursor solution on SS/ABAD-YSZ/CZO substrates is reported. Two approaches have been developed. In the first method, YBCO filaments were directly deposited on the buffered substrate by piezoelectric printing; and in the second approach, CeO2 tracks were first printed to pattern a subsequently overprinted YBCO film, creating a multifilamentary structure by an inverse technique. Scanning Hall probe measurements have been used to compare the filamentary structures and critical currents achieved by both methods, and a J(c) of up to 3 MA cm(-2) has been obtained at 77 K. For the inverse printing approach, the ac hysteresis losses have been also measured and compared with theoretical models