A production run of 60 melt-textured YBCO trapped field magnets (TFMs), 2 cm in diameter, is reported. The TFMs have pinning centers Y211 and (Pt0.4U0.6)YBa3O6 deposits also damage tracks ions from uranium fission. resulting average at the center seed-side surface 〈BT(r = 0)〉 2.04 T 77 K. rms spread BT 5.9%. TFM samples rejected due to problems with SmBCO seeds totaled ~10%, an additional 2% were lost cracking under magnetic pressure. Methods significantly reduce these losses are discussed....

Ongoing research has increased achievable field in trapped magnets (TFMs) to multi-Tesla levels. This greatly the attractiveness of TFMs for applications. However, it also increases already very difficult problem situ activation and reactivation TFMs. The pulsed zero-field-cool (ZFC) method is used most applications because can be accomplished with much lower power more modest equipment than field-cool activation. critical state model (CSM) been a reliable theoretical tool experimental...

Recent experiments on pulsed-zero field cool magnetization of bulk high Jc YBCO (YBa2Cu3O7-δ) have shown unexpected results. For example, reproducible, non-destructive, rapid, giant leaps (GFLs) to higher penetrated are observed. The observations inconsistent with the critical state model (CSM), in several aspects. Additional been pursued an attempt clarify physics involved observed anomalies. Here, we present experimental results for dependence anomalous features. It is found that sudden...

Flux pinning properties and irreversibility fields Birr(T) of melt-textured YBCO with discontinuous or multiple-in-line-damage (MILD) columnar defects produced by irradiation high-energy U238 ions were studied at a constant matching field B = 10?T for several energy losses between Se 1.67 2.4?keV???1. With increasing length the MILD pins, critical current density jc(H,T) strongly increases along c axis progressively shifts upwards reaching 9?T 77?K. For 2.4?keV???1, pronounced kink is...

Experiments are reported on pulsed activation of zero-field-cooled trapped field magnets (TFMs) containing improved broken-columnar pinning centers (PCs). The YBCO TFMs have J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> ~ 50 kA/cm <sup xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and maximum field, BT,max 2.2 T at 77 K. Several results in disagreement with the well-established Bean model. Essentially full is obtained an applied...

Bi 2 Sr Ca Cu 3 O x (Bi-2223) tapes were processed by the standard powder-in-tube technique, but small amounts of UO4 added prior to processing. Both U-doped and undoped subsequently exposed a reactor spectrum neutrons. Whereas materials show moderate enhancements critical current densities Jc due pinning action fast-neutron-induced collision cascades, in increases factors 10–20 thermal-neutron-induced fission 235U subsequent formation tracks. Since are particularly pronounced, when magnetic...

Results on the enhancement of critical current densities in melt-textured bulk (Y-123) superconductors, which were doped with and exposed to thermal neutron irradiation create fission tracks, are presented. These all originate from U-containing clusters a stable UPtYBaO compound, form isotropic `starlike' defects diameters approximately 10 nm lengths . However, if we consider projections onto symmetry plane flux line lattice allow for certain tilt modulus , their pinning-effective size is...

This team has designed, built, and successfully run a radial flux high temperature superconductor (HTS) trapped field magnet (TFM) motor. The motor was in zero cooled mode. paper conveys several lessons learned about the use of TFMs generator applications. state art bulk TFM material is reviewed. Attention given to difficulties activating practical machine design. are based upon (i) cooling time needed field-cool TFMs; (ii) maximum which can be produced at rotor using only MMF on stator;...

We have examined levitation forces of field cooled (2.3 T) and zero YBa2Cu3O7−δ superconductors opposed by a SmCo magnet. achieved unusually large (140 N) pressures (44.6 N/cm2) in measurements. 5–10 subsequent cycles, approach retreat the magnet, result 10–20% decrease force, which then stabilizes.

Columnar pinning centres provide the largest potential, Upin, but not greatest Jc or pinnable field, Bpin. Characteristics of ion-generated columnar defects which limit and Bpin are discussed, including reduction percolation path, need for a larger number columns damage, pinning, than usually estimated. It is concluded that to less 4 T, also severely reduce Jc. The goal maximizing via centres, appears have obscured more rewarding approach resulted in neglect large regime ion interactions....

We introduce a novel approach to x-ray scattering studies in applied magnetic fields by exploiting vortices superconductors. This method is based on trapping flux small disk-shaped superconductor (known as trapped field magnet, TFM) with single-crystal sample mounted or at close proximity its surface. opens an unrestricted optical access the and allows be precisely along momentum transfer, facilitating polarization-sensitive experiments that have been impractical impossible perform date. The...

We discuss an experiment on large-grain YBCO, the intent of which is to compare effectiveness continuous columnar pinning centres (CCPC) that discontinuous aligned centres, in their ability increase Jc. find far superior. The motivation and design are reviewed. High-energy heavy ions were utilized produce damage controlled morphology. resulting Jc presented as a function variable Se, closely related discontinuity diameter damage. dependence magnetic field, temperature, Fi (the number ion...

Large grains of high temperature superconducting (HTS) material can be utilized as trapped field magnets (TFMs). Persistent currents are set up in the HTS when it is cooled a magnetic field, or exposed to after cooling. TFMs have been improved over past two decades by efforts large number worldwide research groups. However, applications using lagged, part due problem fields needed for activation. We describe herein experiments designed observe behaviour TFM activation repeated low (called...

The transport critical current densities, Jc, of superconducting (Bi, Pb)2Sr2Ca2Cu3Ox/Ag tapes were measured before and after employing a special radiation technique, which leaves the grain boundary properties largely unaffected. We identify two regions separated by temperature dependent crossover field Hgb−p. In low region, Jc is limited currents across boundaries, remain unchanged irradiation. Above Hgb−p, flux pinning. this artificial defects optimize pinning enhance Jc.