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ST194 - A New Generation of in situ MgB2 Wires with Improved Jc and Birr Values Obtained by Cold Densification (CHPD)
A New Generation of in situ MgB2 Wires with Improved Jc and
Birr Values Obtained by Cold Densification (CHPD)
René Flükiger, Md. Shahriar Al Hossain, Carmine Senatore,
Florin Buta and Matt Rindfleisch
Abstract - By means of Cold High Pressure Densification (CHPD), the critical current density, Jc , of binary and alloyed MgB2 wires has been enhanced by more than a factor 2 at 4.2K and at fields up to 19 T. The relative MgB2 mass density of binary MgB2 wires
was enhanced to ~ 54 % after applying 2.5 GPa at 300 K before reaction. In C4H6O5 (malic acid) alloyed wires, densification also caused the enhancement of Birr , as a consequence of a slightly enhanced C content, determined by X ray diffraction. Almost
isotropic Jc values were obtained for C4H6O5 added wires of 1 x 0.6 mm2 cross section, the values of Jc(4.2K)=1x104 A/cm2 for parallel and perpendicular fields being obtained at 13.8 and 13.4 T, respectively (1 μV/cm criterion). The corresponding values for 20K were both close to 6.2 T. The value of Birr// at 20K was 11 T. The positive effects of cold densification on Jc and Birr on MgB2 was also observed on 150 mm long wires alloyed with C4H6O5 or with SiC, by the succession of 6 overlapping pressure steps. This process can be extended to long wire lengths: by means of a newly developed prototype machine with an automatic press/release/advance sequence, a first wire length of 1 m was densified at 1.5 GPa, yielding Jc(4.2K) = 1x104 A/cm2 at 13.1 T. Further improvements are expected after optimization.
Index Terms - MgB2, cold densification, critical current density, upper critical field, electrical resistivity.
IEEE/CSC & ESAS European Superconductivity News Forum (ESNF), No. 14, October 2010
The published version of this manuscript appeared in IEEE Transactions on Applied Superconductivity 21, Issue 3, 2649 - 2654 (2011)