We fabricated in situ powder-in-tube processed MgB 2 /Fe tapes using aromatic hydrocarbon of benzene, naphthalene, and thiophene as additives, and investigated the superconducting properties. We found that these aromatic hydrocarbons were very effective for increasing the Jc values. The Jc values of 20mol% benzene-added tapes reached 130A/mm 2 at 4.2K and 10T. This value was almost comparable to that of 10mol% SiC -added tapes and about four times higher than that of tapes with no additions.Microstructure analyses suggest that this Jc enhancement is due to both the substitution of carbon for boron in MgB 2 and the smaller MgB 2 grain size.The MgB 2 superconductor is expected to be applied to practical superconducting wires because its transition temperature, 39K, is much higher than those of conventional metallic superconductors.The lower cost of the raw materials, Mg and B, than that of Nb, is an additional advantage of MgB 2 .Recently, small coils using MgB 2 wires have been produced. In order to evaluate the potential of MgB 2 for power applications, wire processing techniques are now being actively developed throughout the world. The most popular method is the so-called in situ powder-in-tube (PIT) method,

We fabricated powder-in-tube MgB2/Fe tapes using a powder mixture of nanometer-size Mg and commercial amorphous B and investigated the transport properties. High-purity nanometer-size Mg powder was fabricated by applying the thermal plasma method. 5–10 mol % SiC powder doping was tried to enhance the Jc properties. We found that the use of nanometer-size Mg powder was effective to increase the Jc values. The transport Jc values of the nondoped and 10 mol % SiC-doped tapes prepared with nanometer-size Mg powder reached 90 and 250 A/mm2 at 4.2 K and 10 T, respectively. These values were about five times higher than those of the tapes prepared with commercial Mg powder.

This paper reports on the fabrication and testing of an MgB2 coil made by a wind and react method. We made a 130 m-long Fe/Cu-composite sheathed MgB2-superconducting round wire applying an in situ PIT method. Using a 58 m-long wire, we fabricated a small solenoid coil with 459 turns. The Ic of the coil were measured under different external fields and temperatures. Excellent correspondence of Ic between the short sample and the coil was obtained at 4.2 K and in external fields above 4 T. This indicates that the 58 m-long wire has a very homogeneous Ic distribution. At 25 K this coil generated a maximum magnetic field of 1 T (Ic = 100 A, overall-Jc = 200 A mm−2) in an external field of 0.5 T. At 4.2 K this coil generated 1.9 T (Ic = 184 A, overall-Jc = 366 A mm−2) in the external field of 0.5 T. These results demonstrate the possible use of an MgB2 superconducting coil for superconducting magnet applications such as in MRI.

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