Reel-to-Reelシステムを用いたPLD-GdBa2Cu3Oy線材の高速成膜 及び高Ic化技術

PLD-RE1Ba2Cu3Oy (REBCO) coated conductors (CCs) manufactured using a reel-to-reel (RTR) system are inexpensive, can be produced in long lengths and have a high critical current (Ic), making them an excellent choice for industrial applications such as cables, transformers and superconducting magnetic energy storage (SMES) devices. Reducing the approach gap between the target and substrate (dT-S) is one effective technique to increase the production rate for CCs made using the RTR system. Generally, the critical current density (Jc) of PLD-REBCO CCs using a RTR-system decreases as dT-S decreases, because the amount of dead layer, such as a-axis-oriented grains, increases and the composition of the superconductor becomes off-stoichiometic. We speculated that the formation of a-axis-oriented grains in PLD-REBCO CCs fabricated at a short dT-S is due to a high deposition rate (i.e., high supersaturation). In this work, we fabricated PLD-Gd1Ba2Cu3Oy (GdBCO) CCs using a RTR system by varying the target composition and moving speed, to control superconductor composition, and suppress the formation of a-axis-oriented grains. As a result, the PLD-GdBCO CCs have the following characteristics: Ic=312 A/cm-width (Jc=2.6 MA/cm2) with a 1.2 µm thickness and 1 m length when manufactured at 2 m/h (deposition area = 1-turn×6.5 cm = 6.5 cm2, laser power = 300 mJ, ƒ=4-plums×30 Hz). This production rate and Jc value are 3.0 times and 1.8 times higher, respectively, compared to those before controlling the target composition and moving speed. We suggest that our technique is effective for not only increasing the production rate, but also enhancing the Jc of PLD-REBCO CCs manufactured using the RTR system.