IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 19, NO. 3, JUNE 2009 3231 The Development of Second Generation HTS Wire at American Superconductor Xiaoping Li, MartinW. Rupich, Cornelis L. H. Thieme, M. Teplitsky, Srivatsan Sathyamurthy, E. Thompson, D. Buczek, J. Schreiber, K. DeMoranville, J. Lynch, J. Inch, D. Tucker, R. Savoy, and S. Fleshler Abstract—Second Generation (2G) YBCO High Temperature Superconductor wire, based on the RABiTS/MOD process, is now being produced in continuous lengths at American Supercon- ductor (AMSC) using a full-scale, reel-to-reel manufacturing line. AMSC’s approach for manufacturing 2G wire is designed around a low-cost, wide-strip technology, in which a 4-cm wide strip is slit into multiple narrower wires, then laminated to metallic stabi- lizers producing a 3-ply wire called 344 superconductors. A major advantage of this approach is the ability to tailor the electrical, mechanical and thermal properties and dimensions of the final wire for specific applications and operating conditions. This allows the final wire properties to be tuned for targeted applications, including cables and fault current limiters, by tailoring the resis- tivity and thickness of the stabilizer layers. The superconducting properties of the MOD-based YBCO are also being improved by the introduction of thicker YBCO layers and improved flux pinning centers. This paper describes the present status of 2G wire manufacturing at AMSC, reviews present and projected performance of the 344 superconductors, and summarizes initial application demonstrations utilizing 344 superconductors. Index Terms—Coated conductors, HTS, RABiTS, YBCO, 2G wire. I. INTRODUCTION S ECOND generation (2G) high temperature supercon- ducting (HTS) wires have moved out of the laboratory and are now being produced in the quantity, and with the performance, required for large-scale commercial application demonstrations. 2G wire is now supplanting first generation (1G) HTS wire, based on a multifilamentary composite in a silver matrix, in most HTS-based wire applications [1]–[3]. Two major advantages of the 2G technology pioneered by AMSC, over the first generation (1G) HTS wire, include lower cost and the ability to tailor the wire properties and dimensions for specific applications [4]. In this paper, we describe AMSC’s progress in transitioning the 2G wire process from an R&D “pre-pilot”-scale to high Manuscript received August 25, 2008. First published June 30, 2009; current version published July 15, 2009. This work was supported in part by the US Department of Energy, the Office of the Secretary of Defense-Title 3. The authors are with American Superconductor, Devens, MA 01434, USA (e-mail: xli@amsc.com; mrupich@amsc.com; cthieme@amsc.com; mteplitsky@amsc.com; ssathyamurthy@amsc.com; ethompson@amsc.com; dbuczek@amsc.com; jschreiber@amsc.com; kdeMoranville@amsc.com; jlynch@amsc.com; jinch@amsc.com; dtucker@amsc.com; rsavoy@amsc. com; sfleshler@amsc.com). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TASC.2009.2020570 Fig. 1. Schematic illustration of the “wide-strip” manufacturing process for manufacturing low-cost 2G wire at AMSC. volume, production-scale manufacturing and review the prop- erties of the initial 2G HTS wire being produced in AMSC’s production-scale facility. II. AMSC’S 2G “WIDE-STRIP”MANUFACTURING PROCESS AMSC’s approach to manufacturing 2G HTS wire is based on the RABiTS/MOD technology using a “wide-strip” manu- facturing process [2], [4]. For initial operation of the full-scale production equipment, we have chosen to use 4-cm wide strips. The “wide-strip” manufacturing process, illustrated in Fig. 1, relies on the deformation-texturing of a metal alloy (Ni5at%W) substrate and recrystallization in a reel-to-reel system to form a cube-textured alloy template [5], [6]. The buffer layers, con- sisting of a 75 nm thick seed layer, a 75 nm YSZ barrier layer and a 75 nm cap layer are deposited by high-rate reactive sputtering. A rare earth doped YBCO precursor film is slot-die coated onto the buffered substrate at a loading of 4800 mg of template (calculated thickness of 0.8 ), pyrolyzed at and con- verted to an epitaxial film at 750–800 in a reel-to-reel system. The YBCO strip is capped with a Ag layer, and oxygenated at . The Ag coated strip is then slit to the desired width and laminated between two metallic stabilizer strips to form the superconducting wire. The standard wire product, called 344 superconductors (Fig. 2), is prepared from a 4-mm slit ‘insert wire’ and has equivalent dimensions to the First Generation (1G) BSCCO HTS wire. The composition of the stabilizer strip is indicated by the addition of a letter to the wire name, i.e. 344B of brass and 344S for stainless steel. The “wide-strip” process is designed to be inherently low- cost and has the flexibility to produce wire with varying dimen- sions and properties which can be tailored for specific applica- 1051-8223/$25.00 © 2009 IEEE