Upper critical fields of powder-in-tube-processed MgB2/Fe tape conductors

We measured the upper critical field, B-c2, of pure and SiC-added MgB2/Fe tapes prepared by the powder-in-tube process. We found that the B-c2 of the MgB2 tapes was much higher than the B-c2 of MgB2 single crystals. At 4.2 K, the B-c2 of the 10 mol % SiC-added MgB2 tape reached 22.5 T. This B-c2 was almost equal to the B-c2 of a conventional bronze-processed Nb3Sn conductor. At 20 K, the B-c2 of the 5 mol % SiC-added tape was around 10 T, which was comparable to the B-c2 of commercial Nb-Ti at 4.2 K. These results indicate that powder-in-tube-processed MgB2 tape is promising not only for high-field applications but also for applications at 20 K with a convenient cryo-cooler. (C) 2004 American Institute of Physics.