The effect of copper additions in the synthesis of in situ MgB2 Cu-sheathed wires

Electromagnetically Assisted Densification of Copper-Sheeted in Situ MgB 2 /Cu Wires

“…5b) without distinct large regions of dark contrast. This effect can be attributed to Cu addition [5] and was found to be noticeable even for 1 at.% copper addition [8]. The lattice parameters of MgB 2 obtained by XRD measurement and Rietveld refinement vary only slightly between samples, and any significant Cu atomic substitution in MgB 2 can be excluded.…”

“…This XRD results show that after a deliberate addition to the core of 3 at.% of Cu powder, the resulting amount of copper reacted to the MgCu phases is lower than that in the case with no added Cu. This does not stop the reactive diffusion of Cu from the wire sheath to the wire core, but it seems to decrease the final amount of Mg-Cu phases (basically MgCu 2 ) in the core, which results from both added copper and that diffused from the sheath [5]. The fractions of MgO and unreacted B in the wire cores are not greatly affected by the copper addition, although some decrease in both phases can be noticed for sample with Cu powder addition.…”

“…This first method has already a potential to decrease high volume fraction of Mg-Cu phases mixed with MgB 2 in the core after reaction [4,6]. Further and more substantial decrease in Mg-Cu phases and therefore increase in MgB 2 phase fraction in the wire core can be obtained by combining the first method with copper powder addition to the wire core as reported in [5,7]. A wire sample representing this second J c improvement method with an addition ofin pressure waves, which locally create very high pressure, strain and strain rates [14].…”

Modelling of transient state phenomena of composite superconducting conductors during pulse Ic(B) measurements

“…The Cryo-BI-Pulse system and technique was previously described in [2][3][4][5][6]. The system delivers magnetic field and current pulses by the discharge of capacitor banks.…”

“…However, large discrepancies -especially at low magnetic fields -were observed between DC and pulse measurements for a larger-diameter NbTi/CuMn/Cu wire (Luvata OK3900) with a more resistive CuMn interfilamentary matrix (figure 7) [6,7]. The critical current of NbTi/CuMn/Cu wire measured by pulsed techniques was very much lower than the DC value: the apparent critical current measured on a short straight sample was less than half of the DC critical current below 1T.…”