Using uniformly splayed pinning landscape as a tool in the family of Hg-based cuprate superconductors, we (i) demonstrate that such splayed correlated disorder pins vortices stronger in materials with higher anisotropy and (ii) find a consistent description of this systematic trend through an effective rescaling scheme. This scheme demonstrates that in highly anisotropic superconductors extended pinning defects need not be aligned for optimal pinning.

Strong vortex pinning by fission-induced uniformly splayed columnar tracks in anisotropic mercury cuprates is demonstrated to result from (re)scaling of the pinning landscape by a large superconducting anisotropy. The effective "narrowing" of the splay distribution restores variable range vortex hopping (VRH) motion expected for nearly parallel pins. VRH emerges as a distinctive peak in the vortex creep rate (similar to 12% at low fields at T/T-c similar to 0.5) of the most anisotropic HgBa2Ca2Cu3O8+delta, a peak well described by a glassy dynamics with the characteristic exponent mu similar to 1/3. [S0031-9007(98)07526-7].

For the successful application of high-temperature copper oxide superconductors, the problem of the ease of motion of magnetic vortices (quantized flux lines) within the material must be solved. The motion results in finite electrical resistance which prevents the desired loss-free conduction of current1. We demonstrate a solution to this problem by anchoring the vortices with crystallographic defects induced by fission of mercury atoms in a mercury/copper oxide superconductor.

We demonstrate a method by which we expand the useful range of cuprate superconductors to above 100 K and enhance persistent currents by orders of magnitude in fields of several Tesla — namely fission of Hg nuclei within Hg-cuprates with 0.8 GeV protons. The fission process allows “doping” these cuprates with strongly pinning splayed columnar defects. The technique could be technologically relevant, since it is not limited by the short penetration range of heavier particles (or ions) and could permit modification of larger superconducting objects, such as magnets.

High-energy spallation neutron sources are now being considered in the US and elsewhere as a replacement for neutron beams produced by reactors. High-energy and high intensity neutron beams, produced by unmoderated spallation sources, open potential new vistas of neutron radiography. We discuss the basic advantages and disadvantages of high-energy neutron radiography, and consider some experimental results obtained at the Weapons Neutron Research (WNR) facility at Los Alamos.

This article surveys the formation and effects of “tailored” defects, having controlled numbers and several different morphologies, in high temperature superconductors. Defects can affect the equilibrium properties, such as the superconducting length scales ξ (the coherence length) and λ (the London penetration depth). Very importantly, defects provide vortex pinning that supports the conduction of a macroscopic current density. The article introduces these topics and illustrates them with specific examples.

Composite Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8//Ag tapes were irradiated with 0.8 GeV protons to create splayed columnar defects in the superconductor. The resultant effective pinning of vortices leads to an enhanced persistent current density in the CuO planes, displacement of the irreversibility line to higher temperatures and magnetic fields, and a major reduction in the logarithmic time decay rate of the supercurrent density.< >

The isoscalar giant quadrupole resonance is studied in /sup 118/Sn(..pi../sup + -/,..pi../sup + -/') at 130 MeV. It is found that the ratio of ..pi../sup -/ to ..pi../sup +/ cross sections at their maximum is 1.9 and that 57% of the energy-weighted sum rule is exhausted in ..pi../sup -/ scattering. This large ratio of ..pi../sup -/ to ..pi../sup +/ cross sections is not anticipated by conventional models, and may be interpreted as evidence for substantial isovector strength.