Superconducting Wire Substitution

Of course when high temperature superconducting is talked about the “high temperature” is about -140°C. For quite some time the only superconductors with critical temperatures near this point were the cuprates, containing copper and oxygen layers between other superconducting metals. In 2006 it was found that iron compounds, more specifically iron reacted with an oxygen group element, called pnictides, also displayed high temperature superconductivity. This was quite surprising as it is generally believed that iron could not produce the cooper pairs necessary for superconductivity. This discovery has yet to be fully explained in a theoretical way and debates still rage over the exact nature of iron superconductors.

However one of the great fortunes of physics is that luckily we don’t need to fully understand something before we begin applying it. People learnt how to sail long before Archimedes came along and started explaining water displacement. So this paper has aimed to study the positives and negatives of replacing classical superconducting wires in high power electromagnets with some new iron based high temperature ones instead. Niobium-tin (Nb3Sn) is what is normally used due to the cost effectiveness and the easy manufacture of these wires. The suggested substitute is 122 iron arsenide (AE-Fe2As2, AE is any alkali earth metal and 1:2:2 is the ratio of elements) which can sustain the precence of a large magnetic field without losing its superconductivity. The particular superconductor being tested was BaFe2As2 which was doped to remove electrons (P-doping). This superconductor did very well surpassing common alternatives such as magnesium diboride and niobium-titanium in critical current density and reaching the same level as Nb3Sn at field strengths greater that 20 tesla, although in most engineering circumstances this is rarely reached. In a few more years it may be possible to start replacing all superconducting wires with their high temperature alternatives but this would come down to a calculation about whether the effort of manufacture is worth it to save on the cooling process not being as arduous.

Paper links: High-field transport properties of a P-doped BaFe2As2 film on technical substrate

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