Critical currents of Rutherford MgB₂cables compacted by two-axial rolling

Abstract

Two types of Rutherford cables made of two strand layers of commercial MgB2 wires manufactured by Hyper Tech Research, Inc. have been made. Flat rectangular cables consisting of 12 single-core MgB2/Nb/Cu10Ni, or 6-filaments MgB2/Nb/Cu strands, both of diameter 390 mewm, were assembled using a back-twist cabling machine with transposition length of 20 mm. In order to analyze impact of the cable compaction on critical currents, cables were two-axially rolled, each by a single step reduction of 3.5%−29.7% to thickness range of 0.775−0.62 mm. It was found that by increasing the packing factor (PF) of cable above 0.79, the critical current begins to increase. It is improved nearly two times up to the PF limit 0.89. Compaction over the PF limit introduced cable degradation and decrease of critical current. Bending tests applied to cables showed that critical current degradation starts below the bending diameter 120 mm for 6-filaments Cu sheath and 70 mm for single-core Cu10Ni sheath cable. Tensile tests showed similar irreversible strain values for the both types of cables. Rutherford cables assembled of single-core strands are promising for low field (2.7−4 T) applications where low bending diameters are required.

Quench dynamics in MgB2Rutherford cables

“…The wires were manufactured by HyperTech Research and the cabling was performed in the Institute of Electrical Engineering of Bratislava. The cabling procedure and the superconducting properties of Rutherford cable and wire are described in detail in [8]. Both analysed samples, RC-1 and RC-2, of length 11 cm, come from the same cable and therefore have similar manufacturing procedure, except that RC-1 was heat treated at 650 °C with a bend diameter of 80 mm and subsequently straightened, while RC-2 was directly heated in straight form.…”

“…Later on, the interest in Rutherford cables was extended to other superconducting materials and applications. In this way, cables that allows higher operating magnetic fields and/or temperatures, based on Nb 3 Sn [2,3], Bi 2 Sr 2 CaCu 2 O 8+x [4,5,6], and more recently MgB 2 [7,8] and coated conductors [9], have already been developed. Certainly, the specific mechanical, chemical and physical characteristics of the superconducting wires or tapes used for cabling create particular challenges and impose different cabling strategies.…”

“…Since Rutherford cables based on MgB 2 have just been recently proposed [7,8] and are not yet fully developed, it is important to understand their behaviour to further optimize their superconducting properties while providing the required thermal stability for the different applications. The present work aims to analyse the quench dynamics of MgB 2 Rutherford cables, especially focussing on the quench induced by a local heat disturbance.…”

Characterization of <inline-formula> <tex-math notation="LaTeX">${YBa}_{2}{Cu}_{3}{O}_{7-\delta}$</tex-math> </inline-formula> Films With Various Porous Structures Grown by Metalorganic Decomposition Route

“…MOI can also be used for characterising superconducting samples for power cable applications, such as Rutherford cables. Kopera et al [20] have investigated such a cable consisting of 12 wires twisted together. Each of the 12 wires is an MgB 2 cable covered by a layer of Nb, which in its turn is covered by an outer layer of Cu 10 Ni.…”

“…MgB 2 has advantages, such as a high j c and available cost-effective synthesis techniques, and in Ref. [20] it is mentioned that for low-field applications cables make it easier to scale up currents, improve bending tolerance and reduce AC-losses. MOI is a useful technique that provides valuable information about the local magnetic and superconducting properties in such samples.…”