Critical current, flux pinning, and hysteretic loss in round multifilamentary Bi:2212/Ag strands

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Advances in Cryogenic Engineering

OSTI ID:482058

Sumption, M D; Collings, E W ^[1]; Galanski, G ^[2]

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1. Ohio State Univ., Columbus, OH (United States)
2. IGC Advanced Superconductors Inc., Waterbury, CT (United States); and others

Magnetization, hysteresis loss, irreversibility field (H{sub r}), and pinning potential (U{sub 0}) measurements have been made over a wide temperature range on cylindrical {open_quotes}high-J{sub c}{close_quotes} and {open_quotes}low-J{sub c}{close_quotes} Ag-sheathed Bi:2212 multifilamentary strands with the measuring field (H) applied transversely to the strand axis. Over most of the measuring temperature range H{sub r}(T) was found to follow the relationship b.exp({minus}T/T{sub f}) characteristic of a partially coupled layered structure. A comparison of H{sub r}(T) for the wire with H{sub r,{parallel}}(T) and H{sub r,{perpendicular}} (T) for a monocrystal indicated that the strands, although (a-b)-textured in planes parallel to the axis, are c-axis isotropic in the azimuthal plane. Critical state analysis justified the location of H{sub r}(T) midway between H{sub r,{parallel}}(T) and H{sub r,{perpendicular}}(T). The magnetic J{sub c} results were indicative of extreme bridging in the finest filament stands, the presence of which suppressed all signs of eddy current loss at least at field ramp rates, dH/dt, of up to 700 Oe/s. Flux creep was investigated by the standard magnetization-decay approach and also in terms of a creep-moderated dependence of hysteretic loss on dH/dt. The creep-determined values of pinning potential, U{sub 0}, were found to be comparable for both the {open_quotes}high-J{sub c}{close_quotes} and the {open_quotes}low-J{sub c}{close_quotes} strands indicating that transport J{sub c} in the strands was dominated by factors other than elementary pinning; they were presumably micro-structural in nature.

• DOE Contract Number: FG02-92ER81461
• OSTI ID: 482058
• Report Number(s): CONF-950722--
• Journal Information: Advances in Cryogenic Engineering, Journal Name: Advances in Cryogenic Engineering Vol. 42B; ISSN 0065-2482; ISSN ACYEAC
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BISMUTH OXIDES
CALCIUM OXIDES
COPPER OXIDES
CRITICAL CURRENT
HIGH-TC SUPERCONDUCTORS
HYSTERESIS
MAGNETIC FLUX
MAGNETIZATION
SILVER
STRONTIUM OXIDES
SUPERCONDUCTING WIRES