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The large cross-sectional aspect ratio of YBCO coated conductors leads to a large magnetization loss in an AC transverse magnetic field. In this work, the magnetization loss of a multifilamentary YBCO coated conductor was studied experimentally. A 100 mm length of striated multifilamentary YBCO coated conductor was prepared where the conductor and filaments were 10 mm wide and 0.4 mm wide, respectively. Striations in the sample were accomplished by laser ablation. The magnetization loss of this striated conductor as well as a reference non-striated conductor was measured in AC transverse magnetic fields normal to the conductor at various frequencies. The measured magnetization loss of the 100 mm striated conductor was less than 9% of the measured loss of the non-striated conductor at f = 11.3 Hz and H/Hcc = 8.8 (Hcc = Ic/πwc; Ic: critical current, wc: conductor width). Even though the coupling loss component increases the magnetization loss in the striated conductor, the AC loss reduction by striation is still apparent even at 171.0 Hz. The transverse resistance between filaments estimated by a four-probe measurement was 38 µΩ for 1 m at 80 K. The coupling length estimated using this transverse resistance is much longer than the sample length even at 171.0 Hz, suggesting that the filaments in the striated conductor are far from ‘completely coupled’ or ‘saturated’.

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We present the results of numerical analysis of a model of normal zone propagation in coated conductors. The main emphasis is on the effects of increased contact resistance between the superconducting film and the stabilizer on the speed of normal zone propagation, the maximum temperature rise inside the normal zone, and the stability margins. We show that with increasing contact resistance the speed of normal zone propagation increases, the maximum temperature inside the normal zone decreases, and stability margins shrink. This may have an overall beneficial effect on quench protection quality of coated conductors. We also briefly discuss the propagation of solitons and development of the temperature modulation along the wire.PACS numbers: 74.72.-h, 85.25.-j, 05.65.+b, 05.45.-a, 74.90.+n arXiv:0909.5209v1 [cond-mat.supr-con]

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this bu den estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YY) AFRL-PR-WP-TP-2006-201 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Propulsion Directorate Air Force Research Laboratory Air Force Materiel Command Wright-Patterson AFB, OH 45433-7251 SPONSORING/MONITORING AGENCY ACRONYM(S)AFRL-PR-WP SPONSORING/MONITORING AGENCY REPORT NUMBER(S) AFRL-PR-WP-TP-2006-201 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. C 2005 IOP Publishing Ltd. This work is copyrighted. One or more of the authors is a U.S. Government employee working within the scope of their Government job; therefore, the U.S. Government is joint owner of the work and has the right to copy, distribute, and use the work. All other rights are reserved by the copyright owner. SUPPLEMENTARY NOTES ABSTRACTAC losses of YBCO coated conductors are investigated by calculation and experiment for the higher frequency regime. Previous research using YBCO film deposited onto single-crystal substrates demonstrated the effectiveness of 'striping' or filamentary subdivision as a technique for AC loss reduction. As a result of these studies the idea of subdividing YBCO 'coated conductors' (YBCO, overlayer, and even underlayer) into such stripes suggested itself. The suggestion was implemented by burning grooves into samples of coated conductor using laser micromachining. Various machining parameters were investigated, and the striping and slicing characteristics are presented. Loss measurements were performed on unstriped as well as striped samples by the pick-up coil technique at frequencies from 50 to 200 Hz at field sweep amplitudes of up to 150 mT. The effect of soft ferromagnetic Fe shielding was also investigated. The results of the experiments form a starting point for a more general study of reduced-loss coated conductor design (including hysteretic, coupling, normal eddy current, and transport losses) projected into higher ranges of frequency and field-sweep amplitude with transformer and allcryogenic-motor/generator applications in mind. As a result of these studies the idea of subdividing YBCO 'coated conductors' ...

A controlled introduction of second-phase Y 2 BaCuO 5 (211) nanoparticles into YBa 2 Cu 3 O 7−␦ (123) thin films was achieved for the first time for the purpose of increasing flux pinning. The island-growth mode of 211 on 123 was utilized to obtain an area particle density >10 11 cm −2 of 211 thick-disk-shaped nanoparticles in individual layers. Composite layered structures of (211 y nanoparticles/123 z )×N were deposited by pulsed laser deposition on LaAlO 3 substrates, with N bilayers ‫ס‬ 24 to 100, y thickness ‫ס‬ 1 to 2 nm, and z thickness ‫ס‬ 6 to 15 nm (assuming continuous layer coverage). With 211 addition, the critical current densities at 77 K were higher at magnetic fields as low as 0.1 T and increased as much as approximately 300% at 1.5 T. The superconducting transition temperature was reduced by approximately 2 to 4 K for 211 volume fraction <20%. Reinitiation of 123 growth after every 211 layer resulted in a smooth and flat surface finish on the films and also greatly reduced surface particulate formation especially in thicker films (∼1 m).

Y Ba 2 Cu 3 O 7 − x (YBCO) films with nanoparticles of BaSnO3 (BSO) were processed using pulsed laser ablation of a special target made with dual phase sectors of YBCO and BSO. Transport critical current density (Jct) of these YBCO+BSO films in applied magnetic fields and angular dependence of Jct on the applied field orientation was measured. It was observed that in the YBCO+BSO films, the Jct (H‖c orientation) increased considerably as compared to regular YBCO films and was 1.3 times higher than Jct in H‖ab orientation. Cross-sectional transmission electron microscopy images on YBCO+BSO films showed the presence of high density (3.5×1011cm−2) of nanoparticles (∼10nm size) and nanocolumns that extended throughout the thickness of the films with high density of dislocations and stacking faults (1000μm−2). The observed results of enhancements in Jct in H‖c and Jct in H‖ab orientations were discussed in the light of the observed microstructural details.