Damage caused by magnetic pressure at high trapped field in quasi-permanent magnets composed of melt-textured YBaCuO superconductor

Ren, Yanru; Weinstein, R.; Liu, J.; Sawh, Ravi‐Persad; Foster, C.C.

doi:10.1016/0921-4534(95)00398-3

Cited by 322 publications

(151 citation statements)

References 12 publications

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“…[4,5] Cracking of the samples was found to limit the trapped field of bulk YBCO at temperatures below 77 K which can be explained by tensile stresses that occur during the magnetization process due to the stored flux density gradient and may exceed the tensile strength of the material. [6] The mechanical properties of bulk YBCO and its tensile strength can be improved considerably by the addition of Ag. [7,8] Another possibility to avoid cracking during magnetizing is to encapsulate the bulk YBCO disks in steel tubes.…”

mentioning

confidence: 99%

Superconducting bulk magnets: Very high trapped fields and cracking

Gruss

Fuchs

Krabbes

et al. 2001

Applied Physics Letters

160

109

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Improved trapped fields are reported for bulk melt-textured YBa2Cu3O 7−δ (YBCO) material in the temperature range between 20 K and 50 K. Trapped fields up to 12.2 T were obtained at 22 K on the surface of single YBCO disks (with Ag and Zn additions). In YBCO mini-magnets, maximum trapped fields of 16 T (at 24 K) and of 11.2 T (at 47 K) were achieved using (Zn + Ag) and Zn additions, respectively. In all cases, the YBCO disks were encapsulated in steel tubes in order to reinforce the material against the large tensile stress acting during the magnetizing process and to avoid cracking. We observed cracking not only during the magnetizing process, but also as a consequence of flux jumps due to thermomagnetic instabilities in the temperature range betweeen 20 K and 30 K. 7460Ge, 7462Bf, 7480BjBulk type II superconductors can trap high magnetic fields that are generated by superconducting persistent currents circulating macroscopically within the superconductor. The main features of the resulting field distribution are a maximum trapped field B 0 in the center of the superconducting domain and a field gradient towards the sample edge which is determined by the critical current density j c of the supercurrents. Therefore, high trapped fields B 0 in bulk superconductors require a high critical current density and a large size of the current loops. Large single-domain bulk YBa 2 Cu 3 O 7−δ based (YBCO) samples can be produced by melt texture processing, especially by using SmBa 2 Cu 3 O 7−δ (Sm-123) as a seed crystal.[1] The pinning effect in melt textured samples can be improved by irradiation methods [2,3] and alternatively, by zinc-doping. [4,5] Cracking of the samples was found to limit the trapped field of bulk YBCO at temperatures below 77 K which can be explained by tensile stresses that occur during the magnetization process due to the stored flux density gradient and may exceed the tensile strength of the material.[6] The mechanical properties of bulk YBCO and its tensile strength can be improved considerably by the addition of Ag. [7,8] Another possibility to avoid cracking during magnetizing is to encapsulate the bulk YBCO disks in steel tubes. [9] A steel tube leads to stress compensation by generating a compressive stress on YBCO after cooling from 300 K to the measuring temperature which is due to the higher thermal expansion coefficient of steel compared to that of YBCO in the a, b-plane. Maximum trapped fields B 0 of 11.5 T at 17 K and of 14.4 T at 22 K were reported for single YBCO disks and mini-magnets consisting of two single YBCO disks, respectively. [9] In both cases, Ag was added to the YBCO disks which were placed into austenite Cr-Ni steel tubes. Previous attempts to combine the two beneficial effects of Ag and Zn additions failed due to the solubility of Zn in Ag in oxygen atmosphere. High trapped fields have also been reported for bulk Sm-123 with additions of Ag. At the surface of Sm-123 disks, trapped fields of 2.1 T at 77 K and of 8 T at 40 K have been observed. [10] In the present paper, t...

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confidence: 99%

Superconducting bulk magnets: Very high trapped fields and cracking

Gruss

Fuchs

Krabbes

et al. 2001

Applied Physics Letters

160

109

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“…Fig. 1(b) is a similar sample, which has been cracked under magnetic pressure [7]. We note that at the time of the measurement the applied field was removed.…”

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confidence: 97%

A non-destructive, non-contact, quality test of critical current for Ag-BiSCCO tape

Gandini

Weinstein

Parks

et al. 2003

IEEE Trans. Appl. Supercond.

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Abstract-An accurate noncontact method of characterizing Ag-BiSCCO tape is reported, using the trapped field, , of a field-cooled tape. The dimensions of the tape make it possible to calculate in closed form a very simple expression, relating trapped field to transport current. Short lengths of tape, 4 (cm), are used to experimentally confirm the model. The model applies to any length of tape for which length is greater than 5 times the tape width. A schematic of a proposed test apparatus is presented which should permit on-line testing for magnitude of the current, and for cracks, while the tape is in motion during production.Index Terms-BiSCCO tape, critical current density, high temperature superconductors, trapped magnetic field.

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“…Ren et al 4 presented the experimental results and an expanded theory to explain the damage phenomenon in bulk superconductors. Fuchs et al 20 also observed the cracking of YBa 2 Cu 3 O 7−δ samples.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3] However, the low thermal conductivity and poor mechanical stability limit their ability of trapping larger fields. [4][5][6] By improving the thermal stability and the internal mechanical strength, Tomita et al 7 measured that very high trapped magnetic flux density up to 17.24 T were achieved at 29K in bulk YBa 2 Cu 3 O 7−y samples. Recently, Durrell et al 8 reported a trapped field of 17.6 T at 26K in a stack of two silver-doped GdBCO superconducting bulk samples reinforced with shrink-fit steel.…”

Section: Introductionmentioning

confidence: 99%

Kim model for flux-pinning-induced stress in a long cylindrical superconductor

Zeng

Wang

et al. 2016

AIP Advances

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In this work, the flux-pinning-induced stress distribution in a circular cylinder of hightemperature superconductors is studied by adopting the Kim critical state model to describe the relationship between the magnetic flux density and induced current. Based on the plane strain approach, the analytic expressions of the radial and hoop stress in the cylinder are derived for the zero-field cooling and field cooling magnetization processes. It is shown that the stress distributions depend on the activation processes and the values of the dimensionless parameter p in the Kim model, and the overall maximums of the stresses appear at or near the center of the cylinder where cracking may be most likely initiated. In addition, the Kim model has wider applicability than the Bean model, and the influence of p on the stress depends on the activation process.

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Damage caused by magnetic pressure at high trapped field in quasi-permanent magnets composed of melt-textured YBaCuO superconductor

Cited by 322 publications

References 12 publications

Superconducting bulk magnets: Very high trapped fields and cracking

Superconducting bulk magnets: Very high trapped fields and cracking

A non-destructive, non-contact, quality test of critical current for Ag-BiSCCO tape

Kim model for flux-pinning-induced stress in a long cylindrical superconductor

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