44. HIGH TEMPERATURE SUPERCONDUCTING (HTS) SECOND GENERATION WIRE
Substantial worldwide advances have been achieved in recent years with respect to the development and processing of second generation, high temperature superconducting coated conductors (also known as “2G wires”). Compared to first generation wires, these coated conductors have the potential of providing lower cost and higher performance. These wires also provide the possibility of operation at moderate magnetic fields in liquid nitrogen as well as high fields at lower than liquid nitrogen temperature. For short laboratory-scale samples, very high current carrying capacities over 1,000 A/cm at 77K have been reported. Pre-commercial coated conductors, longer than 300 meters and with current-carrying capacity over 200 A/cm, also have been demonstrated. Nonetheless, further innovation and development will be needed to achieve the DOE vision for commercial availability of 2G wires that have a cost/performance ratio as low as $10/kA-m (dollars per kiloampere-meter) and can be fabricated in practical forms. Grant applications are sought only in the following subtopics:
a. Effect of Filament Geometry on AC Loss—For practical ac applications, ac loss from 2G conductor remains a concern. Although superconductor filamentization has been shown to be a proven method of AC loss reduction in low temperature superconducting and first generation high temperature superconducting wires, present 2G wires instead consist of a continuous layer of Rare-Earth1Ba2Cu3Ox superconductor. In addition, the current-stabilizer layer, which is in direct contact with the superconductor, is also continuous. It would be advantageous to establish how various filament shapes, arrangements, and geometries affect the AC loss of 2G conductors. Therefore, grant applications are sought to determine the influence of superconductor filament shape, arrangement, and/or geometry on AC loss using potentially scaleable filamentization methods. Approaches of interest include: (1) detailed studies of reduced-loss coated conductor designs, including hysteretic, coupling, eddy current and transport losses projected over broad ranges of frequencies and field-sweep amplitudes; and (2) the development of scalable, cost-effective continuous methods to filamentize the superconducting and stabilizing layers.
Questions – contact Harbans Chhabra (harbans.chhabra@hq.doe.gov)
b. Low Aspect-Ratio Coated Conductors—Traditional superconducting wires are typically round or of low aspect-ratio. On the other hand, present 2G tapes are of high aspect-ratio, a geometry does not lend itself to twisting, which is a proven way to reduce AC loss. In addition, for wide tapes, gaps can result during winding, which further increases loss. Therefore, grant applications are sought to develop innovative approaches to obtain low aspect-ratio conductors using present 2G tapes, or to develop low-cost templates that are of natural low aspect-ratio. Approaches of interest include: (1) innovations for the scalable fabrication of low aspect-ratio or round-wires using present 2G tapes; (2) the determination of the characteristics of such wires, including transport, AC loss, and mechanical and tape-to-tape interaction; and (3) novel substrate fabrication methods that can result in low aspect-ratio or rounded templates.
Questions – contact Harbans Chhabra (harbans.chhabra@hq.doe.gov)
c. Cryogenic Dielectric Materials that can be Integrated into 2G Conductors—The lack of appropriate cryogenic dielectric materials is one of the barriers to the commercial application of superconductors. For 2G conductors, wrapping with dielectric tapes is a costly, time consuming, and potentially conductor-damaging approach. Grant applications are sought to identify and develop high-performance, cryogenic dielectric materials, and to develop low-cost scalable methods to integrate such dielectrics into the 2G conductor architecture as coatings. Approaches of interest include: (1) the identification and characterization (with respect to dielectric strength, partial discharge behavior, mechanical and thermal compatibility, under cryogenic conditions) of existing high performance dielectric materials that can potentially be integrated into 2G conductors by scalable methods; and (2) the development of novel dielectrics with enhanced cryogenic performance.
Questions – contact Harbans Chhabra (harbans.chhabra@hq.doe.gov)
d. Novel Ultra-Fast Techniques to Deposit Epitaxial Layers for Low-Cost 2G Conductors—One of the major factors that inhibits rapid throughput, and hence increases the cost, of 2G conductors is the moderate deposition rate of buffers and high temperature superconducting films. Thus far, the approach has been to increase the deposition area using moderately-rapid deposition techniques. Grant applications are sought to develop methods for ultra-fast deposition rates (for example, greater than 10 nanometers per second) for the production of highly textured epitaxial films (buffers and/or superconductor). By the end of Phase II, the proposed research project should demonstrate not only ultra-fast deposition but also that the deposited buffer or superconductor is capable of sustaining high current density.
Questions – contact Harbans Chhabra (harbans.chhabra@hq.doe.gov)
References:
1. Ashworth, S. P. and Grilli, F., “A Strategy for the Reduction of AC Losses in YBCO Coated Conductors,” Superconductor Science and Technology, 19(2): 227-232, February 2006. (ISSN: 0953-2048) (Abstract and ordering information available at: http://www.iop.org/EJ/journal/SUST. Scroll to bottom of page to search for article.)
2. Sumption, M. D., et al., “AC Loss in Striped (Filamentary) YBCO Coated Conductors Leading to Designs for High Frequencies and Field-Sweep Amplitudes,” Superconductor Science and Technology, 18(1): 122-134, January 2005. (ISSN: 0953-2048) (Abstract and ordering information available at: http://www.iop.org/EJ/journal/SUST. Scroll to bottom of page to search for article.)
3. Nishioka, T., et al., “AC Loss of YBCO Coated Conductors Fabricated by IBAD/PLD Method,” IEEE Transactions On Applied Superconductivity, 15: 2843-2846, 2005. (ISSN: 1051-8223) (Summary available at: http://www.ascinc.org/asc04/Format.asp?paperNumber=4ML03&Category=2)
4. Duckworth, R. C., et al., “Substrate and Stabilization Effects on the Transport Ac Losses in YBCO Coated Conductors,” IEEE Transactions On Applied Superconductivity, 15: 1583-1586, 2005. (ISSN: 1051-8223)
5. Hammerl, G., et al., “Possible Solution of the Grain-Boundary Problem for Applications of High-Tc Superconductors,” Applied Physics Letters, 81(17): 3209-3211, October 2002. (ISSN: 0003-6951)(Abstract and ordering information available at: http://apl.aip.org/)
6. Cao, Y., et al., “The Future of Nanodielectrics in the Electric Power Industry,” IEEE Transactions on Dielectrics and Electrical Insulation, 11: 797-807, 2004. (ISSN: 1070-9878)
7. Nelson, J. K., and Hu, Y., “Nanocomposite Dielectrics-Properties and Implications,” Journal of Physics D: Applied Physics, 38(2): 213-222, January 2005. (ISSN: 0022-3727) (Abstract and ordering information available at: http://www.iop.org/EJ/abstract/0022-3727/38/2/005. Scroll to bottom of page to search for article.)
8.
Paranthaman, M. P., and Izumi, T., “High-Performance YBCO-Coated
Superconductor Wires,” MRS Bulletin, 29(8): 533-589, August 2004.
(Abstract and ordering information available at:
http://www.mrs.org/s_mrs/sec_subscribe.asp?CID=3009&DID=131712.)
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