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

Abstract

We measured the upper critical field, Bc2, of pure and SiC-added MgB2/Fe tapes prepared by the powder-in-tube process. We found that the Bc2 of the MgB2 tapes was much higher than the Bc2 of MgB2 single crystals. At 4.2 K, the Bc2 of the 10 mol % SiC-added MgB2 tape reached 22.5 T. This Bc2 was almost equal to the Bc2 of a conventional bronze-processed Nb3Sn conductor. At 20 K, the Bc2 of the 5 mol % SiC-added tape was around 10 T, which was comparable to the Bc2 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.

Carbohydrate doping to enhance electromagnetic properties of MgB2 superconductors

“…2 These record high properties have been confirmed and reproduced by many groups, 2,5,10,11 and the performance records remain unbroken up to now. However, the best high-field J c values achieved in the SiC doped MgB 2 wires were compromised by the reduction in self-field and low-field J c .…”

“…1͒ and the high critical current density ͑J c ͒ of Ͼ10 5 cm −2 in moderate fields, magnesium diboride ͑MgB 2 ͒ superconductors could offer the promise of important largescale applications to be operated at 20 K. A significant enhancement in the electromagnetic properties of MgB 2 has been achieved through doping with various forms of carbon ͑C͒. [2][3][4][5][6] To take advantage of its T c of 39 K, enhancements of both the upper critical field ͑H c2 ͒ and J c are essential. Attempts to accomplish this have invoked the introduction of numerous techniques including chemical doping, [2][3][4][5][6] irradiation, 7 and various thermomechanical processing techniques.…”

“…[2][3][4][5][6] To take advantage of its T c of 39 K, enhancements of both the upper critical field ͑H c2 ͒ and J c are essential. Attempts to accomplish this have invoked the introduction of numerous techniques including chemical doping, [2][3][4][5][6] irradiation, 7 and various thermomechanical processing techniques. 8,9 Chemical doping is a simple and readily scalable technique.…”

Microscopic role of carbon on MgB2 wire for critical current density comparable to NbTi

“…The field dependence of the critical current measured by the standard four-probe method is shown in Figure 1a. Compared with other types of carbon doping, such as SiC doping, [26][27][28][29] the malic acid-doped sample studied in this work not only shows increased high-field critical current density, but also increased low-field critical current density, even comparable to that of NbTi, exceeding 10 5 A cm À2 at 4.2 K and 6 T. At higher temperature, for example at 20 K, the critical current density of SiC-doped samples has been reported to be decreased compared with the un-doped samples, but here, even at 20 K, the critical current density was increased.…”

Enhanced flux pinning in neutron irradiatedMgB2

“…The important role of grain boundaries as pinning centers has been emphasized. 2 The intentional addition of defects such as nano-particles 3,4 and irradiation damages 5 has been proved to be effective in enhancing both B c2 and flux pinning, but a unambiguous discrimination between these two effects has not been formulated yet.…”