M. Igarashi

High-speed deposition of high-quality RE123 films by a PLD system with hot-wall heating

We have studied the use of a hot-wall heating system for producing GdBa2Cu3O7?X (Gd123) films with large critical current (Ic), stably, at high speed, by a pulsed laser deposition (PLD) method. We achieved a material yield from the PLD system with hot-wall heating of about 50% through optimization of the evaporation conditions. With the PLD system, we were able to fabricate a Gd123 film about 20?cm long with a high Ic of 997?A (77?K, self-field) at about 6??m thickness. The maximum Ic that we achieved for a Gd123 film about 2?cm long was 1040?A (77?K, self-field) at about 6? ?m thickness. Furthermore, we were able to form a Gd123 film about 1? ?m thick and 20?cm long with an Ic of 352?A (77?K, self-field) at a high speed of 60? m?h?1 using high laser power. For the production of long conductors coated with RE123 (REBa2Cu3O7?X, where RE stands for rare earth) using hot-wall heating, it was found that RE123 coated conductors over 100?m long with Ic of over 200?A had uniform Ic distributions with ? 2% variations in the direction of the length.

Remarkable progress in fabricating RE123 coated conductors by IBAD/PLD technique at Fujikura

Increase of production rate and improvement of quality for RE123 coated conductors have been tried. In-plane texturing of MgO was attempted by the IBAD system with the world largest ion source. As a result of optimizing condition in large deposition area, the dramatically high throughput of 1000 m / h was realized to obtain the IBAD-MgO with Δ 600 A except some locations was obtained at the throughput of 15 m / h. In addition to the speed-up, the very high Ic of 1040 A was also achieved by the hot-wall heating PLD system.

Long-length GdBCO coated conductors with IBAD/PLD method

We fabricated a long-length GdBCO(GdBa2Cu3O7-?) coated conductor by the ion-beam assisted deposition (IBAD) and the pulsed laser deposition (PLD) methods. The GdBCO tape was over 400 m in length with 1.5-2.0 MA/cm2 of the critical density. The critical currents of the tape were over 304.8 A/cm along 368 m in length. So we have achieved Ic ? L = 112,116 Am. For the IBAD process, we have already developed 500 m-length IBAD-Gd2Zr2O7 (IBAD-GZO) tapes with highly aligned in-plane texture, and continuously fabricate 250 m-length tapes at a rate of 0.5~1 km/month. In addition, we have also developed a new type template for the IBAD-GZO, to enable the production rate fast. Structure of the template is IBAD-GZO/IBAD-MgO/Y2O3. It is note that MgO (111) is parallel to the substrate normal and three fold symmetry. For this structure, the film thickness of the IBAD-GZO could lessen from 1.2 ?m to 0.3 ?m. By the new IBAD buffer layer, a production rate is expected to be over 30 m/h.

Development for Mass Production of Homogeneous RE123 Coated Conductors by Hot-Wall PLD Process on IBAD Template Technique

Recent development of production technique for RE123 coated conductors was reviewed, using Hot-wall PLD/ IBAD process. Lot-to-lot distributions for both average value and longitudinal uniformity of Ic at 77 K, 0 T were summarized for 127 run of 300-500-m-long 10-mm-wide CC. By optimizing hotwall PLD process parameters we found a reproducible high Jc production condition (20% enhancement in field at 20 K), less angular dependent to applied magnetic field. Furthermore, new hermetic type Cu stabilization foil configuration was developed and general mechanical properties against tensile strain, etc. were surveyed.

Progress in Scale-Up of RE-123 Coated Conductors With

By an IBAD/PLD method, a 500 m-length high-performance GdBa₂Cu₃O_x (GdBCO) coated conductor with BaZrO₃ (BZO) was fabricated. End-to-end I_c of the 503.5 m tape was 349.6 A/cm at 77 K, corresponding I_c times L value of 176,023 Am. New approaches to decrease the thickness of IBAD buffer layers were developed by combination of IBAD-MgO(111) and IBAD-Gd₂Zr₂O₇ (GZO). The maximum Jc of the GdBCO on the buffer layer was 550 A/cm. We also started to investigate IBAD-MgO(OOl) by using a large IBAD system with a 110 cm times 15 cm ion source. A 50 m-length IBAD-MgO tape with DeltaPhi of 13deg was fabricated at a 100 m/h-1 pass. Insulated REBCO wires with Cu or Ni-Cr lamination were developed using 5 mm-wide conductors sliced from 10 mm-wide IBAD/PLD tapes. Practical long insulated wires were supplied for several prototypes of motors, transformers and fault current limiters in fiscal 2007.

I_{c}

REBa2Cu3Ox (REBCO, RE = rare earth) coated conductors (CCs) are expected to show high performance for superconducting coil applications due to their high tensile strength and high critical current density under magnetic fields. One of the most serious problems on the coil application is the significant screening current, which is caused by the configuration of CC. Since screening current is dependent on the width of the REBCO layer, filamentization of the REBCO layer is strongly desired. We have succeeded in fabricating long length four-divided multifilamentary CCs with 4 mm wide over 100 m long by using the process of scratching the IBAD-MgO layer (scratching process). In this work, we fabricated two epoxy-impregnated coils and investigated the effects of the screening current. One of the coils is wound with multifilamentary CCs fabricated by scratching process, another is wound with conventional mono-filamentary CC. As the results, it is confirmed that the screening current is reduced and the coupling current between the filaments might be in the acceptable range on the DC magnet application.