Munetsugu Ueyama

Microstructures and Jc-B Characteristics of Ag-Sheathed Bi-Based Superconducting Wires

We prepared silver-sheathed BiPbSrCaCuO wires by the powder-in-tube method. Maximum critical current densities at 77.3 K were 5.4×10 4 A cm -2 in a zero magnetic field, 4.2×10 4 A cm -2 at 0.1 T and 1.2×10 4 A cm -2 at 1 T. K, as the J c improves, the history effects decrease. J c and J c -B enhancements are due to the decrease and dispersion or nonsuperconducting phases, and to grain boundary improvements

Magnetic field dependence of critical current density in Bi - Pb - Sr - Ca - Cu - O silver sheathed wire

Abstract BiPbSrCaCuO silver sheathed high Tc superconducting wires were fabricated through the solid reaction process. It is proposed in this paper that the magnetic field dependence of Jc of the wire is dominated by the Lorentz force perpendicular to the c-axis, caused by a transport current with c-axis component crossing grain boundaries, when a magnetic field is applied parallel to the plane of the wire. It was found that BiPbSrCaCuO silver sheathed wire had sufficient potential for applications at 4.2 K. The history effect of Jc for high Jc specimens was not observed at 77.3 K and appeared again at 4.2 K

Development of silver-sheathed bismuth superconducting wires and their application (invited)

The development results for silver‐sheathed bismuth (2223 phase) superconducting wires in the past two years have suggested that three different fields of application will be feasible in the very near future. The first field is large current conductor application in liquid nitrogen operation. The second is magnet application (relatively low magnetic field below 1 Tesla, such as for semiconductor crystal pulling and magnetic separation) in liquid nitrogen operation. The third is super‐high field application above 20 Tesla in liquid helium operation. In this paper, we will describe the state of the art of high‐Tc superconducting wires using a combination of bismuth high‐Tc phase and powder‐in‐tube technique. Maximum Jc at 77.3 K reached to 53 700 A/cm2 in a zero magnetic field, 42 300 A/cm2 at 0.1 Tesla and 12 000 A/cm2 at 1 Tesla. Prototypes, such as a 1000 A carrying conductor at 77.3 K, a 1000 Gauss coil at 77.3 K and a super‐high field coil at 4.2 K were made and tested successfully.

High field generation using silver-sheathed BSCCO conductor

Abstract A J c (77 K) of a 1200 m long silver-sheathed bismuth-based superconducting wire has reached 10 900 A/cm 2 . The performance of application prototypes has also got a great deal of progress. For example, a 60 mm bore BSCCO magnet generated 4 T at 4.2 K, 3 T at 21 K, and stably generated 2.5 T at 21 K for over 150 h when cooled with GM refrigerator. This magnet has a practical-sized winding bore of 60 mm, and a 40 mm RT bore cryostat was installed for actual application. Also. high magnetic field properties of another BSCCO magnet having a 40 mm winding bore were evaluated with a backup field up to 22.54 T at 4.2 and 27 K. The maximum fields generated by a backup hybrid magnet and BSCCO coil was 24.0 and 23.4 T at 4.2 and 27 K, respectively.

Silver-sheathed Bi(2223) wire and application

Among many high- T c oxide superconductive materials and processing technologies, a combination of the bismuth high-T c phase and the powder-in-tube technique is revealed to be useful for long-wire fabrication and many applications in various fields, such as large current conductors, cryogenic current leads and magnets. Maximum J c at 77.3 K reached 53 700 A/cm 2 in a zero magnetic field, 42 300 A/cm 2 at 0.1 T and 12 000 A/cm 2 at 1 T. Maximum J c of multifilamentary wire at 77.3 K reached 15 400 A/cm 2 . A 30 m long wire with a multifilamentary structure was fabricated. J c over the whole length of this wire was 5190 A/cm 2 at 77.3 K. Results of prototypes were summarized and revealed that many applications in a wide temperature range from 4.2 to 77.3 K will be feasible in the near future.

Generation of 24.0 T at 4.2 K and 23.4 T at 27 K with a high‐temperature superconductor coil in a 22.54 T background field

The 4.2 K and 27 K current‐carrying performance of a high‐temperature superconducting (HTS) coil was measured in background fields up to 22.54 T generated by a hybrid magnet (Hybrid III) at the MIT Francis Bitter National Magnet Laboratory. The coil, 40 mm winding i.d., 108 mm winding o.d., and 113 mm high, consists of 17 double pancakes, each wound with silver‐sheathed BSCCO‐2223 tapes. Each pancake is the product of a react‐and‐wind method. In total, the test coil contains ∼1200 m of BSCCO‐2223 conductor weighing ∼7 kg. Prior to the measurements in Hybrid III, the coil was tested in zero background field in the temperature range from 4.2 to 77 K. It was coupled to a Gifford–McMahon type cryocooler and at 15 K generated a peak field of 2.1 T; at 18 K, it generated 1.9 T, operating continuously for ∼50 h. In a 22.54 T background field of Hybrid III, the coil reached critical currents of 116.5 A ([Jc]sc, critical current density based on the BSCCO cross‐sectional area only, of 261 A/mm) at 4.2 K and 67 A (...

Development of Bi Based Superconducting Wires

Long length high-strength alloy sheathed Bi2223 tapes were developed. The tolerance for tensile stress improved to twice as high as that of the silver sheathed tape. Length and Jc at 77K of the tape achieve 800m and 30kA/cm2 respectively. The long length tape was coated with Poly-vinyl formval, and successfully insulated along the overall length without any Jc degradation. Special samples to study AC losses were fabricated and investigated. The samples consist of successfully separated filaments without any bridging. And twisting gives an obvious loss reduction especially in the external magnetic field parallel to the tape plane.

Development of High-Tc Superconducting Magnet Using Ag-Sheathed Bi2223 Tapes

We have succeeded in developing two types of the refrigerator cooled High-Tc superconducting magnets; 4-Tesla and 7-Tesla types. They have the same inner diameter of 80 mm and outer diameter of 292 mm, but the coil height was increased to 200 mm of 7-Tesla type from 68 mm of 4-Tesla type. The 4-Tesla type successfiilly produced the central magnetic field of 4.0 Tesla over 30 minutes and 3.5 Tesla for 48 hours. High ramp rate excitation up to 0.35 Tesla per second was achieved, which was a hundred times faster than that of the refrigerator-cooled magnets using the metallic superconductors. The 7-Tesla type magnet stably generated 7.1 Tesla over 24 hours and was excited at a rate of 2 Tesla per minute.

Transport critical current properties of silver-sheathed Bi-based superconducting tapes and coils at 4.2 K

Transport critical current properties of silver-sheathed bismuth-based superconducting tapes and coils were investigated at 4.2 K and up to 25 T. Critical currents showed isotropic properties when the direction of the applied magnetic field changed from parallel to the tape surface to perpendicular, i.e., Jc of 8.9×104 A/cm2 for H//tape and 6.6×104 A/cm2 for H⊥ tape at 23 T. Critical current properties of a three-double-pancake coil were consistent with those of short specimens, showing little change at from 5 to 23 T.

AC Loss Characteristics of Silver Sheathed Bi-2223 Multifilamentary Wires

Inductive method using a pickup coil system was carried out to study AC loss of the silver sheathed Bi-2223 multifilamentary wires in the AC external magnetic field. AC losses of the untwisted and twisted specimens were measured and compared with that calculated according to Been model. The advanced wires including oxide barrier among the inter-filaments space were also manufactured.