Koji Muranaka

Development of RE123 coated conductor by ISD method

Abstract High rate deposition of HoBa2Cu3O7−δ (HoBCO) layers using the pulsed laser deposition method were experimented for long high temperature superconducting (HTS) coated conductor. Laser conditions and oxygen ambient during HoBCO deposition were precisely inspected. This revealed that the deposition rate of HoBCO reached to 5 μm/min. Even at such high deposition rate, the Jc of HoBCO films remained over 105 A/cm2 on the biaxial buffered substrate fabricated by the inclined substrate deposition (ISD) method. Moreover continuous tape production equipments were installed to make a long and flexible coated conductor by ISD method. These equipments will enable us to fabricate of over 100 m long coated conductor. 55 m long coated conductor were fabricated by using these equipments as our first trial of long length fabrication. Evaluation of Jc distributions of 55 m coated conductor revealed that all parts of 1 m in the 55 m conductor had the Jc over 104 A/cm2.

Thin Film YBCO Tape with Over 3 meter Length Fabricated by Inclined Substrate Deposition

We have employed the inclined substrate deposition (ISD) method in order to get a biaxially textured YBCO film [1,2]. For verification of high producibility of ISD method, we have been trying to fabricate YBCO tapes with several meter lengths using the Reel-to-Reel continuous deposition system. The X-ray pole figure measurement revealed that ISD buffer layers and YBCO layers on them were in-plane aligned over 3 meter long. The YBCO tape had the high Jc value of more than 104 A/cm2 at 77.3K over 3 meter length.

Development of Ag-sheathed Bi(2223) superconducting wires and coils

Abstract Silver-sheathed Bi(2223) superconducting wires with long length and high J c of over 10 4 A/cm 2 at 77.3 K in a zero magnetic field were developed by using the powder-in-tube method, and the performance of many application prototypes has progressed. For long wires, a multifilamentary structure is effective for good flexibility and it is easy to handle the long wire without degradation of superconducting properties. We have fabricated the prototype of a refrigerator-cooled magnet with the react and wind technique. This magnet has been operated at 21 K and generated 3.0 T in a 40φ mm room temperature bore (60 φ mm winding bore) and 2.5 T continuously for over 150 h.

Bi-Based Silver-Sheathed High-Tc Superconducting Wire and Application

The application of high temperature superconducting wire will be feasible with the improvement in the critical current density and the development of the hundred-meter class flexible wire.

2.1 Tesla HTSC Magnet Cooled by Refrigerator

We have been developing silver-sheathed bismuth(2223) superconducting wires using the powder-in-tube method and their applications. After obtaining high-Jc properties with silver-sheathed bismuth(2223) superconducting wires in 1991, a long-wire fabrication become the key issue for actual application. To date, we have successfully developed long wires over hundred meters with high Jc.

Cryogen -Free 40mm-Bore 1 TESLA BSCCO Magnet Cooled By Refrigerator

A large-bore, 40mm I.D., (Bi,Pb)2Sr2Ca2Cu3O10 high-Tc superconducting magnet was wound by react & wind technique using flexible multifilamentary wire. The magnet was constructed with 12 double-pancake coils and current leads was made of same wire. A Gifford-MacMahon type refrigerator was used to cool the magnet. The magnet successfully generated 1 Tesla, and was stably operated for over a hundred hours at 21K From these results, it can be expected that non-cryogen magnet using a refrigerator will be the near future application of high-Tc superconducting magnet.

Recent Progress in BPSCCO Wire Fabrication and Application Prototypes

A Jc (77 K) of a 1,200 m long silver-sheathed bismuth-based wire has reached 10,000 A/cm2, as evaluated with a strict Ic criterion of 10-14Ω • m for overall wire cross-sectional area. One of the most important issues for Jc enhancement is grain connectability. Differential technique of ZFC (zero field cooling) curves proved to be a simple and effective evaluation method for grain connection. The performance of application prototypes progressed greatly. Three typical examples were as follows; 1) Current leads of 2,000 A carrying capability have been implemented to NbTi bending magnets of superconducting synchrotron radiation facility of Sumitomo Electric, and have been stably operated for over one year from December 1993. 2) Two flexible cable conductors of 1m-length, having Ic (77 K) of 5,800 A (Jc=12,000 A/cm2) and 12,000 A (Jc=11,000 A/cm2), were fabricated with multilayer wound technique. 3)A 60 mm bore magnet, cooled with GM refrigerator down to 21 K, has stably generated 3 T without any cryogen. The size of this magnet was large enough for actual applications.

Microwave Properties of High-Tc Superconducting Film Characterized by Dielectric Resonator

We report studies on surface morphology of RE-Ba2Cu3O7 (RE=Nd, Sm, Gd and Yb) high-Tc superconducting, HTS, thin films on MgO(100) substrates fabricated by laser ablation method and their microwave properties. The microwave properties were measured as the surface resistance (Rs), at 11.9GHz using a microwave dielectric resonator In comparison with each composition of REBa2Cu3O7 films, the three times difference was observed in the grain size of films. The surface morphology of the lowest surface resistance of films which were fabricated in their most suitable conditions was depended on the RE composition.

Microwave Properties of Nd-Ba-Cu-O Film Characterized by Dielectric Resonator

Thin films were deposited on MgO substrates by ablation of a stoichiometric sintered Nd1+xBa2-xCu3Oy (NdBaCuO) target, substituted Ba by Nd ions, using a KrFexcimer laser. The effects of several deposition parameters on the superconducting NdBaCuO thin films, e.g., gas pressure, substrate temperature, and laser power were studied. For measurement of microwave properties, as the parameter x was increased from -0.1 to 0.15, the Rs became gradually reduced. The suitable value of the parameter x was 0.1 to get the lowest surface resistance film of the Nd1+xBa2-xCu3Oy.