(Color online) (a) Shown is a small area of a 1-cm-wide coated conductor divided into 40 stripes. The distance between the centers of the grooves is . The nonsuperconducting grooves are about wide. The width of a superconducting stripe is about . The top layer is silver. (b) Profile of the groove; the depth is about and it extends well into the substrate, cutting through silver, YBCO, and buffer layers.
(Color online) Magneto-optical image of a fully striated sample divided into 20 stripes. The sample was field cooled in to and then the field was turned off. The bright (yellow online) bands correspond to magnetic flux trapped by the superconducting stripes. The dark (green) spaces are nonsuperconducting grooves.
(Color online) (a) Energy loss per meter length, per cycle for different frequencies in the 40-filament sample, plotted as a function of the amplitude of applied field. (b) The same data as in (a) presented as the power loss per meter length vs sweep rate. Also shown is the power loss in the 20-filament sample. For comparison, the values of the power loss in both samples at are indicated.
(Color online) The same data as in Fig. 3(b) presented as power loss per unit of the sweep rate vs sweep rate [see Eq. (8)]. (a) The 20-filament sample and (b) the 40-filament sample. For each sample the hysteresis loss (the -axis intercept) and coupling loss (the slope) are shown and the breakeven rates, and , respectively, are indicated by the arrows.
(Color online) Two multiply connected patterns of the superconducting layer that have been tested. The superconducting area is shown in gray (blue online); the nonsuperconducting cuts are shown by the dark lines. (a) Alternating bridges (brickwall pattern). (b) Parallel bridges (fishnet pattern). The distance between the successive bridges indicated by the arrow is the current-transfer length .
(Color online) (a) Sketch of the multifilament sample with one superconducting bridge at the center; fragment of the fishnet pattern is shown in Fig. 5(b). (b) A small area of the actual 20-filament sample. The length of the sample is , width is , and width of the bridge (about ) is approximately half of the width of an individual stripe. The top layer is silver.
(Color online) Power loss per unit of the sweep rate vs sweep rate [see Eq. (8)] for the 20-filament sample with a bridge at the center, as shown in Fig. 6. The hysteresis loss , the coupling loss , and the breakeven rate are indicated. The straight dashed line is the linear fit to data.
(Color online) (a) A sketch of the sample with alternating bridges (brickwall pattern). The bridges are placed away from the nearest edge. (b) A small area of the actual 20-filament sample. The top visible layer is silver. The width of the bridge (about ) is approximately half of the width of an individual stripe. (c) Profile of the YBCO layer around the bridge. The cap silver layer was etched away.
(Color online) (a) In this photograph a bridge between two stripes in exposed YBCO layer is shown. The width of the stripes is about and the bridge is about wide. (b) The exposed YBCO layer cut in the brickwall pattern with the transfer length of .
(Color online) Images of the film with alternating bridges [same pattern as in Fig. 9(b)]. The sample was cooled in zero field to and then the magnetic field was applied in steps (increased to a maximum of and then decreased back to zero). (a) MO image in external field that is at the start of the cycle. The bright areas correspond to maximum flux density. The arrows point at nonsuperconducting grooves. (b) Optical photograph of the same area. The double arrows indicate one of the three visible rows of bridges in each figure. The distance (along a groove) between successive bridges . (c) MO image of the same area as in (a) after the external field is turned off (end of half cycle). Nonsuperconducting (defective) bridge is encircled.
(Color online) Power loss per unit of the sweep rate vs sweep rate [see Eq. (8)] for the 20-filament sample with alternating bridges, as shown in Fig. 8(a). The hysteresis loss , the coupling loss , and the breakeven rate are indicated. The straight dashed line is the linear fit to data.
(Color online) For comparison, the data for three 20-filament samples with different patterns—fully striated [Fig. 4(a)], fishnet (Fig. 7), and brickwall (Fig. 11)—are shown together. To avoid clutter, only one frequency, , is included.
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