Long HTS Coated Conductor Processed via Large-Area PLD/ABAD for High-Field Applications

Progress in the upscaling of multibeam pulsed laser deposition (PLD) is reported. Tapes 220 m long were repeatedly processed using an extended drum in PLD installation employed for the deposition of ceria cap buffer and YBCO layers. A Cr-Ni stainless steel tape preliminary coated with a biaxially textured yttria-stabilized-zirconia buffer layer via alternating-beam-assisted deposition was used as a substrate. In 2014, the upscaling of the PLD technique was performed in three steps. In the first step, a 22-m-long tape with record "in-field" critical current (500 A in a 4-mm-wide tape at 4.2 K, 18 T, B//c) was achieved in February 2014. The second step enabled the deposition of 110-130-m-long tapes with moderate (20%) reduction of critical current and sufficiently small local dropouts of the current. The third step resulted in the upscaling of tape processing to 230 m in length. First tapes of such length were already obtained in December 2014. Further upscale of the tape length toward 600 m and more is in progress so far. The most important feature of the PLD process is that the critical current in the coated conductors demonstrates no reduction in the end of the tape, which was exposed to a single run of translation of the rotating drum with the tape, i.e., from one end to the other end. Moreover, in many cases, a tendency of increase of critical current was observed during deposition run. Pulses of oxygen pressure formed by the deposition system together with the influence of barium zirconate precipitations enabled rather high in-field critical currents in 230-m-long tapes.