Abrahamsen, Asger Bech

Bednarcik, J.

Eisterer, M.

Grivel, Jean-Claude

Herrmann, M.

Holzapfel, B.

Häßler, W.

Kovac, P.

Kulich, M.

Melisek, T.

Nenkov, K.

Rodig, C.A.S.

von Zimmermann, M.

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 19, 2017Texture induced anisotropy of critical current of MgB2/Fe rolled superconductingtapes studied by synchrotron x-ray diffractionAbrahamsen, Asger Bech; Häßler, W.; Kovac, P.; Eisterer, M.; Herrmann, M.; Rodig, C.A.S.; Nenkov, K.;Holzapfel, B.; Melisek, T.; Kulich, M.; von Zimmermann, M.; Bednarcik, J.; Grivel, Jean-ClaudePublication date:2010Link back to DTU OrbitCitation (APA):Abrahamsen, A. B., Häßler, W., Kovac, P., Eisterer, M., Herrmann, M., Rodig, C. A. S., ... Grivel, J-C. (2010).Texture induced anisotropy of critical current of MgB2/Fe rolled superconducting tapes studied by synchrotron x-ray diffraction. Poster session presented at 40th Danish Crystallographers Meeting and 3rd DANSCATTMeeting, Copenhagen, Denmark.Texture induced anisotropy of critical current of MgB2/Fe rolled superconducting tapes studied by synchrotron x-ray diffractionAsger B. Abrahamsen1, W. Häßler2, P. Kovac3, M. Eisterer4, M. Herrmann2, C. Rodig2, K. Nenkov2, B. Holzapfel2, T. Melisek3, M. Kulich3, M. von Zimmermann5, J. Bednarcik5 and J-. C. Grivel11 Materials Research Division, Risø-DTU, Roskilde, Denmark2 Institute for Metallic Materials, Leibniz-Institute for Solid State and Materials Research, Dresden, Germany3 Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava, Slovakia4 Atomic Institute, Vienna University of Technology, Austria5 Hamburger Synchrotronstrahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron, Hamburg, GermanyResultsFigure 2b shows the rocking curve of theMgB2(200) and (100) reflection for both carbonand un-doped tapes. The intensity was fitted byI ~ V0 σ(hkl)(α) I0 exp(− μFelFe) (1)where V0 is the illuminated volume, σ(hkl)(α) isgiven by the texture distribution, I0 is theincident intensity, μFe is the mass attenuationcoefficient and lFe is the absorption path of theiron sheath. A texture of αt = 27.8 2.2o and αt= 29.3 0.3o was found for un and c-doping.We have correlated the texture of carbon doped MgB2-xCx superconducting grains in Fe tapes to theanisotropy of the critical current density. A percolation model of the transport current of weaklytextured media shows good agreement with the data and illustrates that carbon doping is decreasingthe anisotropy by scattering between the two superconducting energy gaps.Figure 1 a) Critical current of MgB2-xCx tape as the applied magnetic field isrotated from perpendicular to parallel with the tape plane. b) Critical currentof MgB2-xCx tapes as function of the applied magnetic field for both paralleland perpendicular field direction.IntroductionWe have measured the texture of MgB2superconducting grains formed inside Fetubes, which were first filled by a precursorpowder of Mg + 2B + C, rolled flat into atape and finally heat treated at T = 600 oCin Argon for 3 hours[1]. The MgB2 willhave the c-axis of the hexagonal unit cellaligned with the normal of the tapes asillustrated on inset of figure 1. The criticalcurrent of such a tape has a largeanisotropy when a magnetic field is variedfrom perpendicular to in-plane as shownon figure 1a. This is due to the anisotropyof upper critical field of MgB2 which is ofthe order Hc2||ab = 14.5 Tesla and Hc2||c =3.2 Tesla. Figure 1b is showing how thecritical current is decreasing with appliedfield and that the anisotropy is increaseswhen the applied field is larger than Hc2||cfor the un-doped tape. The carbon dopedtape shows very little anisotropy, whichcan be explained by an increasedscattering between the two super-conducting energy gaps of MgB2, but theinfluence of the texture distribution neededto be separated from the gap anisotropy.Texture measurements at BW5 @ DesyBy rotating the tape in a E = 100 keVsynchrotron beam it was possible topenetrate the Fe sheath while collectingthe diffraction pattern from the MgB2 on aMAR345 image plate detector. Figure 2ashows how a Gaussian texture distributionof the form f(α)~exp(- α2 / αt2), where αt isthe width, results in partial Debye Scherrercones.ConclusionA percolation path model of the transportcurrent in MgB2-xCX has been formulatedby M. Eisterer and combined with themeasured texture distributions it describesthe critical current density quite well (solidlines of fig 1b). Thus the change of theanisotropy of the critical current of MgB2-xCX can only be explained as an increasedelectronic scattering between the twoenergy gaps of the superconductor withincreased carbon doping.Indsæt billedeFigure 2 a) Illustration of the Gaussian texture distribution of the c-axisgrains when an incident x-ray beam is parallel with the plane of the tape. Thecutting of the Ewalds sphere in the small angle limit will appear as theintersection with a plane and cause partial Debye Scherrer cones. b)Rocking curve of MgB2 (002) and (100) reflection. Inset scattering geometry.[1] W. Häßler, P. Kovac, M. Eisterer, A.B. Abrahamsen, M. Herrmann,C. Rodig, K. Nenkov, B. Holzapfel, T. Melisek, M. Kulich, M. vonZimmermann, J. Bednarcik and J-.C. Grivel, “Anisotropy of thecritical current in MgB2 tapes made of high energy milled precursorpowder”, Supercond. Sci. Technol. 23 (2010) 065011.T = 4.2 KB = 7.5 TeslaMgBUn-dopedC-doped x = 0.13a)b)a)b)

Texture induced anisotropy of critical current of MgB<sub>2</sub>/Fe rolled superconducting tapes studied by synchrotron x-ray diffraction

http://orbit.dtu.dk/ws/files/6392257/ABAbrahamsen_Danscatt.pdf

Texture induced anisotropy of critical current of MgB<sub>2</sub>/Fe rolled superconducting tapes studied by synchrotron x-ray diffraction

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology