Koso Fujino

Development of in-plane aligned YBCO tapes fabricated by inclined substrate deposition

Abstract High temperature superconducting thin film tapes, which consist of a flexible metal substrate, buffer layer, and Y 1 Ba 2 Cu 3 O x (YBCO) layer have been developed for power application. Ni-alloy tape was used as the substrate. Both the YBCO layer and the buffer layer were formed by pulsed laser deposition (PLD) because of an advantageous of high deposition rate. Inclined substrate deposition (ISD) was developed to introduce in-plane alignment for the buffer layer on the non-textured metal substrate. YBCO films epitaxially deposited on the ISD buffer layer by normal PLD had high J c values over 10 5 A/cm 2 at 77 K. For verification of high rate productivity of the PLD/ISD method, we demonstrated high rate deposition of the yttria stabilized zirconia buffer layer and YBCO superconducting layer. We also performed continuous deposition of over 10 m YBCO thin film tapes with a reel-to-reel substrate transfer system combined with 200 W high power laser equipment.

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.

Development of YBa/sub 2/Cu/sub 3/O/sub y/ tape by using inclined substrate method

YBa/sub 2/Cu/sub 3/O/sub y/ (YBCO) wire has higher critical current density (J/sub c/) and less degradation in J/sub c/ upon application of a magnetic field than (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ (Bi2223) powder-in-tube wire. It has good potential for use as a high temperature superconducting (HTS) wire following Bi2223. For many years, we have been studying a process to form biaxially aligned YBCO film on metal-based tape by the inclined substrate deposition (ISD). To date, we have succeeded in fabricating a 6 m-long YBCO wire by a continuous process of the ISD method. We have also investigated performance of the fabricated YBCO wire and the advantages of YBCO wire in its applications to rectifier-type fault current limiter (FCL) and HTS cable.

A Bi-2223 Layer-Winding Coil Using 540 m Tape Including a Joint Inside the Winding

High Temperature Superconductors (HTS) are now widely used in many applications such as power transmission cables, motors, etc. Recent (Bi,Pb)2Sr2Ca2Cu3Ox(Bi-2223) conductors have been much improved in transport and mechanical properties, and their application as insert coils for high field generation is expected. In order to demonstrate the feasibility and the potential of Bi-2223/Ag tapes for magnet applications, we fabricated a layer-wound coil using Bi-2223/Ag/Cu-alloy tapes. We used two tapes, 330 m- and 210 m-pieces, in order to examine the possibility of extension of conductor length through a lap-joint inside the coil. These two tapes were soldered without removing Cu-alloy laminations. The winding has the dimensions: inner dia. 57.1 mm, outer dia. 88.9 mm, coil height: 153.9 mm, 44 layers (2,355 turns). We tested this coil at 4.2 K in 0 ~ 12 T. The test coil carried 193.3 A (0.1 μV/cm criterion) and generated 3.3 T in the axial direction of the coil in external 12 T (15.3 T in total). The critical current is close to the short sample performance in the perpendicular fields. Splice resistance at the joint stayed about 1 μΩ at 4.2 K, 10 T.

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.

Recent progress of HTS magnet using Bi-2223 Ag-sheathed wire

The authors have succeeded in developing two types of refrigerator cooled high-Tc superconducting magnets-a high magnetic field type and a large bore type. The high magnetic field type has a room temperature bore of 50 mm, an inner diameter of 80 mm and an outer diameter of 300 mm. The coil height is 200 mm, using 24 double pancakes. The magnet generated 7.1 T over 24 hours and was excited at a rate of 7 T/minute. This high ramp rate was ten times faster than that of a refrigerator cooled magnet using metallic superconducting wires. The large bore type magnet has a room temperature bore of 280 mm, an inner diameter of 400 mm and an outer diameter of 520 mm. The coil height is 18 mm using 2 double pancakes. The magnet generated 0.17 T and was excited at a rate of 0.034 T/s. These two types of HTS magnets, produced by using only Bi-2223 Ag-sheathed tapes, have been continuously operated at 20 K for practical applications.

Industrial Applications of HTS Coils Using DI-BSCCO Wire

Applications of the HTS coils are rapidly increasing since the Sumitomos DI-BSCCO HTS wire has been developed and commercialized. This DI-BSCCO wire has almost the same mechanical properties as that of the copper wire while it can load a hundred times current. One of the applications of the HTS coils is the motor for the ship propulsion system. It reduces carbon dioxide emissions and contributes the anti-global warming action. Other application is the high-field magnets for the R&D activities. Fabrication of coils for these applications was carried out without difficulties thanks to its improved mechanical properties. The test results show the effectiveness of the DI-BSCCO wire

Development of HoBCO tapes fabricated by ISD process

Ho/sub 1/Ba/sub 2/Cu/sub 3/O/sub x/ (HoBCO) tapes by using pulsed laser deposition (PLD) have been developed on flexible Ni-alloy substrates. Inclined substrate deposition (ISD) was developed to introduce in-plane alignment for buffer layers. YSZ was deposited by PLD combined with ISD as a buffer layer on Ni-alloy tape. The advantage of ISD is a high growth rate due to the self in-plane alignment without any other assistance. This was demonstrated by using a CeO/sub 2/ buffer layer. A CeO/sub 2/ buffer layer shows high growth rates of 1 - 2 /spl mu/m/min. As for the growth rate of HoBCO, 4 /spl mu/m/min. was confirmed. Scale-up of the PLD system for making a long tape was performed. In this system, a 200 W-KrF excimer laser over 100 h continuous operation, a large deposition chamber including long ramp heater and three 10-in target system, and a reel to reel tape transfer system up to several hundred meters were introduced and combined. The continuous sputtering system for silver layer and O/sub 2/ annealing system were also introduced. By using these systems, a 50 m CeO/sub 2/ buffer was continuously deposited on a Ni-alloy tape. The deposition tape speed was 0.75 m/h, thickness was 2 /spl mu/m, and full-width at half-maximum was 23/spl deg/ in average. By depositing HoBCO on a part of this CeO/sub 2//Ni-alloy tape, Ic = 29 A/cm-width and Jc = 0.27 MA/cm/sup 2/ were demonstrated.

Angular dependence of critical current in YBCO tapes fabricated by inclined substrate deposition

Abstract In this study, the angular dependence of Jc is investigated in detail for YBa2Cu3Oy (YBCO) tape fabricated by the inclined substrate deposition method. The result shows that Jc has a notable peak when the magnetic field is perpendicular to the plane of the tape, which indicates that the tape has lower Jc at medium degrees of the angle of the field to the tapes plane. The peak gradually diminishes as the field increases. This study confirms that data of the perpendicular and the parallel field dependence of Jc, as such, are not sufficient for evaluation of practical performance of YBCO tape.

1 Meter Long Thin Film Tape with High Jc of 1.5 × 105A/cm2 Fabricated by Pulsed Laser Deposition

Long and high Jc YBCO thin film tapes were successfully fabricated using flexible Ni-based alloy substrates by continuous PLD technique. Maximum Jc value of 1.5×105A/cm2(77.3K, 0T) over the whole length of 1 meter was achieved to enhance in-plane alignment of YBCO layer. The Jc value of 3.0×105A/cm2(77.3K, 0T) was obtained for 10cm in length. The best Jc value of 4.3×105A/cm2(77.3K, 0T) was achieved for a short sample. Results of Jc-B measurement and tensile bending test indicated that the in-plane alignment led to excellent durability against external magnetic field and tensile strain.